everything.study
17.484

Comparative Grand Strategy and Military Doctrine

3-0-9 units · Graduate

A comparative study of the grand strategies and military doctrines of the great powers in Europe (Britain, France, Germany, and Russia) from the late 19th to the mid-20th century. Examines strategic developments in the years preceding and during World Wars I and II. What factors have exerted the greatest influence on national strategies? How may the quality of a grand strategy be judged? Exploration of comparative case study methodology also plays a central role. What consequences seem to follow from grand strategies of different types? Open to undergraduates with permission of instructor.

Fall 2004

Topics

  • Course Overview and Introduction to Grand Strategy
  • Material Influences on Strategy: Geographical Position, National Power and Military Technology
  • Military Organizations
  • Nationalism
  • The International Political System: Constraints, Incentives and Interactions
  • Historical Case Studies
  • The Anglo-German Rivalry (Naval and Otherwise)
  • Grand Strategy and Military Doctrine Among the Pre-WWI Land Powers
  • The July Crisis, Military Strategy and the Outbreak of the War
  • The Course and Conduct of WWI
  • British and German Grand Strategy in the 1930s
  • French Grand Strategy
  • Military Doctrine, Land Warfare, and the Crises of the Late 1930s
  • The Opening Battles of the War

Readings

  • LEC #: 1 · TOPICS: Course Overview and Introduction to Grand Strategy · READINGS: Clausewitz, Carl von. “The Influence of Clausewitz.” On War . Edited and translated by Michael Howard and Peter Paret. Princeton: Princeton University Press, 1976, pp. 27-44. Note: All scholars of security affairs should own this book. If you do not wish to own this book, you must copy these pages and read them.
    Reading assignment
  • ———. “War Plans.” On War . Edited and translated by Michael Howard and Peter Paret. Princeton: Princeton University Press, 1976, Book 8, pp. 577-637. Note: All scholars of security affairs should own this book. If you do not wish to own this book, you must copy these pages and read them.
    Listed reading
  • Bassford. “Clausewitz and His Works.” Chapter 2 in Clausewitz in English. pp. 9-33.
    Listed reading
  • Liddell-Hart. Strategy . Chapter XIX, pp. 319-323.
    Listed reading
  • Posen. Sources of Military Doctrine . Chapter 1, pp. 13-33.
    Listed reading
  • LEC #: 2 · TOPICS: Material Influences on Strategy: Geographical Position, National Power and Military Technology · READINGS: Geographical Position and National Power
    Reading assignment
  • Kennedy. The Rise and Fall of British Naval Mastery . Chapter 7, pp. 177-202.
    Listed reading
  • Posen. Sources of Military Doctrine . Chapter 2, pp. 34-41, 59-80.
    Listed reading
  • _Weigley. “A Strategy of Sea Power and Empire.” Chapter 9 in The American Way of War . pp. 167-191. Supplements the preceding.
    Listed reading
  • Military Technology
    Listed reading
  • Howard. “Men Against Fire.” In Military Strategy and the Origins of the First World War . pp. 41-57.
    Listed reading
  • LEC #: 3 · TOPICS: Military Organizations · READINGS: Howard. War in European History . Chapter 4, pp. 54-74.
    Reading assignment
  • Posen. Sources of Military Doctrine . pp. 41-59.
    Listed reading
  • Vagts. History of Militarism . pp. 323-359.
    Listed reading
  • Travers. “Technology, Tactics, and Morale: Jean de Bloch, the Boer War and British Military Theory, 1900-1914.” pp. 264-286.
    Listed reading
  • LEC #: 4 · TOPICS: Nationalism · READINGS: Carr. “The Third Period.” In Nationalism and After . pp. 17-26.
    Reading assignment
  • Stern. “Why do People Sacrifice for Their Nations?” In Perspectives on Nationalism and War . pp. 99-121.
    Listed reading
  • Hayes. “Nationalism and International War,” and “Nationalism and Militarism.” In Essays on Nationalism . pp. 126-155, 187- 195.
    Listed reading
  • Williamson. “The Domestic Context of Habsburg Foreign Policy.” Chapter 2 in Austria-Hungary and the Origins of the First World War . pp. 13-33.
    Listed reading
  • LEC #: 5 · TOPICS: The International Political System: Constraints, Incentives and Interactions · READINGS: Jervis. “Cooperation Under the Security Dilemma.” pp. 167-214.
    Reading assignment
  • Waltz. “Anarchic Orders and Balances of Power,” and “Structural Causes & Military Effects.” In Theory of International Politics . pp. 102-128, 161-193.
    Listed reading
  • Christensen and Snyder. “Chain Gangs and Passed Bucks.” International Organization 44, no. 2 (Spring 1990): 137-168.
    Listed reading
  • Lynn-Jones. “Offense-Defense Theory and its Critics.” Security Studies 4, no. 4 (Summer 1995): 660-691.
    Listed reading
  • LEC #: 6 · TOPICS: Historical Case Studies · READINGS: George. Case Studies and Theory Development . pp. 43-68.
    Reading assignment
  • Levy. “Too Important To Leave to the Other.” International Security 22, no. 1 (Summer 1997): 22-33.
    Listed reading
  • Haber, Kennedy and Krasner. “Brothers Under the Skin…” International Security 22, no. 1 (Summer 1997): 34-43.
    Listed reading
  • Gaddis. “History, Theory and Common Ground…” International Security (Summer 1997): 75-85.
    Listed reading
  • Posen. The Sources of Military Doctrine . Read the Preface, and Chapters 2 and 7, but read them after you read the methodology articles, and with an eye to how methodological problems were solved, or not. You can skim as much of the rest of the book as you wish.
    Listed reading
  • Paret. “The History of War and the New Military History.” In Understanding War. pp. 209-226.
    Listed reading
  • LEC #: 7 · TOPICS: The Anglo-German Rivalry (Naval and Otherwise) · READINGS: Crowe. “Memorandum.”
    Reading assignment
  • Kennedy. “Tirpitz, England and the Second Navy Law of 1900: A Strategical Critique.” pp. 33-57.
    Listed reading
  • ———. Rise and Fall . Chapter 8, pp. 205-237.
    Listed reading
  • Turner. Origins of the First World War . pp. 1-60.
    Listed reading
  • Lynn-Jones. “Détente and Deterrence: Anglo-German Relations, 1911-1914.” In Military Strategy and the Origins of the First World War . pp. 165-194.
    Listed reading
  • Geiss. German Foreign Policy, 1871-1914 . pp. 75-83, 106-118, 121-127, 139-145.
    Listed reading
  • Copeland. “German Security and the Preparation for World War I.” Chapter 3 in The Origins of Major War . Ithaca, NY: Cornell, 2000, pp. 56-78.
    Listed reading
  • Rich. Hitler’s War Aims . pp. XIX-XXX. (useful historical background)
    Listed reading
  • LEC #: 8 · TOPICS: Grand Strategy and Military Doctrine Among the Pre-WWI Land Powers · READINGS: Stevenson. “Militarization and Diplomacy in Europe before 1914.” International Security 22, no. 1 (Summer 1997): 125-161.
    Reading assignment
  • Sagan. “1914 Revisited: Allies, Offense, and Instability.” In Military Strategy and the Origins of the First World War . pp. 109-133.
    Listed reading
  • Ritter. “The Breach of Neutrality.” In The Schlieffen Plan . pp. 3-10, 78-96.
    Listed reading
  • Snyder. The Ideology of the Offensive . (entire)
    Listed reading
  • LEC #: 9 · TOPICS: The July Crisis, Military Strategy and the Outbreak of the War · READINGS: Trachtenberg. “The Meaning of Mobilization in 1914.” In Military Strategy and the Origins of the First World War . pp. 195-226.
    Reading assignment
  • Van Evera. “The Cult of the Offensive.” In Military Strategy and the Origins of the First World War . pp. 59-109.
    Listed reading
  • Turner. Origins . pp. 60-115.
    Listed reading
  • Turner. “The Russian Mobilization in 1914.” pp. 252-268.
    Listed reading
  • Herrmann. The Arming of Europe and the Making of the First World War . Chapter 7, pp. 199-224.
    Listed reading
  • Fuller. “The Battles of the Marne and Tannenberg, 1914.” In A Military History of the Western World . pp. 182-228.
    Listed reading
  • _Recommended _ Levy. “Preferences, Constraints, and Choices in July 1914.” In Military Strategy and the Origins of the First World War . pp. 226-262.
    Listed reading
  • Keegan. “The Somme.” In The Face of Battle . pp. 204-284. Note: This book is a Minor Classic; Security Studies Scholars should own a copy. If you do not wish to own the book or cannot find a library copy you will need to make yourself a copy.
    Listed reading
  • Kennedy. Rise and Fall . Chapter 9, pp. 239-265.
    Listed reading
  • _Recommended _ May. “The U-Boat Campaign.” In The Use of Force, edited by Art and Waltz. pp. 298-315.
    Listed reading
  • The original source is: May. The World War and American Isolation . Cambridge: Harvard University Press, 1966, pp. 114-136. (Students will also find pp. 200-252, and 387-415 instructive.)
    Listed reading
  • Steiner. Britain and the Origins of the First World War .
    Listed reading
  • Berghahn. Germany and the Approach of War in 1914 .
    Listed reading
  • Keiger. France and the Origins of the First World War .
    Listed reading
  • Lieven. Russia and the Origins of the First World War .
    Listed reading
  • Williamson. Austria Hungary and the Origins of the First World War .
    Listed reading
  • Shanafelt. The Secret Enemy . (About German-Austria relations.)
    Listed reading
  • LEC #: 11 · TOPICS: British and German Grand Strategy in the 1930s · READINGS: Weinberg. “From One War to Another.” In A World At Arms . pp. 6-47.
    Reading assignment
  • May. Strange Victory . Chapter 7, pp. 94-110.
    Listed reading
  • Kennedy. Rise and Fall . Chapter 10, pp. 267-298.
    Listed reading
  • Posen. Sources of Military Doctrine . Chapters 5, and 6.
    Listed reading
  • Schweller. “An Assessment of the International Distribution of Power (circa 1938-1940).” Deadly Imbalances . pp. 203-208. (Appendix)
    Listed reading
  • Howard. War in European History. Chapter 7, pp. 116-135.
    Listed reading
  • LEC #: 12 · TOPICS: French Grand Strategy · READINGS: May. Strange Victory . Chapters 8, 9, 10 (pp. 113-153), Chapters 19-21 (pp. 271-322).
    Reading assignment
  • Young, Robert. In Command of France . pp. 1-33.
    Listed reading
  • Posen. Sources of Military Doctrine. Chapter 4.
    Listed reading
  • LEC #: 13 · TOPICS: Military Doctrine, Land Warfare, and the Crises of the Late 1930s · READINGS: Mearsheimer, John. Conventional Deterrence. (All but the Chapter on the Nato-Pact competition.)
    Reading assignment
  • Herwig, Holger. “Clio Deceived.” In Military Strategy and the Origins of the First World War . pp. 262-301.
    Listed reading
  • May. Strange Victory . Chapters 11, 12, pp. 153-212.
    Listed reading
  • Overy and Wheatcroft. “The Soviet Union.” Chapter 5 in The Road To War . pp. 210-257.
    Listed reading
  • LEC #: 14 · TOPICS: The Opening Battles of the War · READINGS: Review
    Reading assignment
  • Posen. Sources of Military Doctrine . pp. 81-104.
    Listed reading
  • May. Strange Victory . Chapters 15, 16, 17, 18 (pp. 215-268), Chapters 24 through to the conclusion (pp. 347-464).
    Listed reading
  • Clausewitz, Carl von. “The Influence of Clausewitz,” and “War Plans.” In On War, edited and translated by Michael Howard and Peter Paret. Princeton, NJ: Princeton University Press, 1976. ISBN: 9780691056579.
    Required
  • Howard, Michael. War in European History . New York, NY: Oxford University Press, Incorporated 2001. ISBN: 9780192802088.
    Required
  • Bassford, Christopher. Clausewitz in English . New York, NY: Oxford University Press, 1994. ISBN: 9780195083835.
    Required
  • Liddell-Hart, Basil H. Strategy . New York, NY: Plume, Incorporated, 1991. ISBN: 9780452010710.
    Required
  • Kennedy, Paul. The Rise and Fall of British Naval Mastery . Amherst, New York, NY: Humanity Books, Publishers, 1986. ISBN: 9781573922784.
    Required
  • Kennedy, Paul M. “The First World War and the International Power System.” International Security 9, no. 1 (Summer 1984): 7-40.
    Required
  • Irvine, Dallas. “The Origin of Capital Staffs.” Journal of Modern History 10 (June 1938): 161-79.
    Required
  • Travers, T. H. E. “Technology, Tactics, and Morale: Jean de Bloch, the Boer War and British Military Theory, 1900-1914.” Journal of Modern History 51 (June 1979): 264-86.
    Required
  • Carr, Edward Hallett. “The Third Period.” In Nationalism and After. London, UK: Macmillan & Co., Ltd., 1945, pp. 17-26.
    Required
  • Stern, Paul C. “Why Do People Sacrifice for Their Nations?” In Perspectives on Nationalism and War, edited by John L. Comaroff and Paul C. Stern, 99-121. New York, NY: Routledge, 1995. ISBN: 9782884491662.
    Required
  • Hayes, C. J. H. “Nationalism and International War,” and “Nationalism and Militarism.” In Essays on Nationalism. New York, NY: Russell & Russell, 1966, pp. 126-55, 187-95.
    Required
  • Paret, Peter. “Nationalism and the Sense of Military Obligation.” Military Affairs 34, no. 1 (February 1970): 2-6.
    Required
  • Posen, Barry R. “Nationalism, the Mass Army, and Military Power.” International Security 18, no. 2 (Fall 1993): 80-129.
    Required
  • Van Evera, Steven. “Hypotheses on Nationalism and War.” International Security 18, no. 4 (Spring 1994): 5-39.
    Required
  • Farrar, L. L., Jr. “Villain of the Peace: Nationalism and the Causes of World War I.” Canadian Review of Studies in Nationalism 22, no. 1-2 (1995): 53-66.
    Required
  • Williamson, Samuel. “The Domestic Context of Habsburg Foreign Policy.” Chapter 2 in Austria-Hungary and the Origins of the First World War . London, UK: Macmillan, 1991, pp. 13-33. ISBN: 0333420810.
    Required
  • Jervis, Robert. “Cooperation Under the Security Dilemma.” World Politics 30, no. 2 (January 1978): 167-214.
    Required
  • Waltz, Kenneth Neal. “Anarchic Orders and Balances of Power,” and “Structural Causes & Military Effects.” In Theory of International Politics. New York, NY: McGraw-Hill, 1979, pp. 102-28, 161-93. ISBN: 9780075548522.
    Required
  • Christensen, Thomas, and Jack Snyder. “Chain Gangs and Passed Bucks.” International Organization 44, no. 2 (Spring 1990): 137-168.
    Required
  • Lynn-Jones, Sean M. “Offense-Defense Theory and its Critics.” Security Studies 4, no. 4 (Summer 1995): 660-691.
    Required
  • George, Alexander. “Case Studies and Theory Development: The Method of Structured, Focused Comparison.” In Diplomacy: New Approaches in History, Theory and Policy, edited by Paul Gordon Lauren, 43-68. New York, NY: Free Press, 1979. ISBN: 9780029180709.
    Required
  • Lijphart, Arend. “Comparative Politics and the Comparative Method.” American Political Science Review 64 (1971): 682-93.
    Required
  • ———. “The Comparable Cases Strategy in Comparative Research.” Comparative Political Studies 8, no. 2 (1975): 158-77.
    Required
  • Levy, Jack. “Too Important To Leave to the Other.” International Security 22, no. 1 (Summer 1997): 22-33.
    Required
  • Haber, Stephen, David M. Kennedy, and Stephen D. Krasner. “Brothers Under the Skin: Diplomatic History and International Relations.” International Security 22, no. 1 (Summer 1997): 34-43.
    Required
  • Gaddis, John Lewis. “History, Theory and Common Ground…” International Security (Summer 1997): 75-85.
    Required
  • Paret, Peter. “The History of War and the New Military History.” In Understanding War . Princeton, NJ: Princeton University Press, 1993, pp. 209-226. ISBN: 9780691000909.
    Required
  • Crowe, Eyre. “Memorandum on the Present State of British Relations with France and Germany,” January 1, 1907. In British Documents on the Origins of the War, 1898-1914, vol. III: The Testing of the Entente, 1904-6, edited by G. P. Gooch and Harold Temperley. London, UK: His Majesty’s Stationery Office, 1928.
    Required
  • Kennedy, Paul. “Tirpitz, England and the Second Navy Law of 1900: A Strategical Critique.” Militargeschichtliche Mitteilungen 2 (1970): 33-57.
    Required
  • Turner, L. C. F. Origins of the First World War. New York, NY: W. W. Norton and Company, Incorporated, 1970. ISBN: 9780393099478.
    Required
  • Lynn-Jones, Sean. “Detante and Deterrence: Anglo-German Relations, 1911-1914.” In Military Strategy and the Origins of the First World War: An International Security Reader, edited by Steven E. Miller, Sean M. Lynn-Jones, and Stephen Van Evera, 165-94. Princeton, NJ: Princeton University Press, 1991. ISBN: 9780691023496.
    Required
  • Geiss, Imanuel. German Foreign Policy, 1871-1914. London, UK: Routledge and Kegan Paul, 1976, pp. 75-83, 106-18, 121-27, 139-45. ISBN: 9780710083036.
    Required
  • Williamson, Samuel R. “Joffre Reshapes French Strategy, 1911-1913.” In The War Plans of the Great Powers 1880-1914, edited by Paul M. Kennedy, 133-54. Boston, MA: Unwin Hyman, 1979. ISBN: 9780049400566.
    Required
  • Copeland, Dale C. “German Security and the Preparation for World War I.” Chapter 3 in The Origins of Major War. Ithaca, NY: Cornell University Press, 2000, pp. 56-78.
    Required
  • Stevenson, David. “Militarization and Diplomacy in Europe before 1914.” International Security 22, no. 1 (Summer 1997): 125-161.
    Required
  • Sagan, Scott. “1914 Revisited: Allies, Offense, and Instability.” In Military Strategy and the Origins of the First World War: An International Security Reader, edited by Steven E. Miller, Sean M. Lynn-Jones, and Stephen Van Evera, 109-33. Princeton, NJ: Princeton University Press, 1991. ISBN: 9780691023496.
    Required
  • Ritter, Gerhard. “The Breach of Neutrality.” In The Schlieffen Plan. New York, NY: Praeger, 1958, pp. 3-10, 78-96.
    Required
  • Snyder, Jack. The Ideology of the Offensive . Ithaca, NY: Cornell University Press, 1989. ISBN: 9780801482441.
    Required
  • Trachtenberg, Marc. “The Meaning of Mobilization in 1914.” In Military Strategy and the Origins of the First World War: An International Security Reader, edited by Steven E. Miller, Sean M. Lynn-Jones, and Stephen Van Evera, 196-226. Princeton, NJ: Princeton University Press, 1991. ISBN: 9780691023496.
    Required
  • Van Evera, Steven. “The Cult of the Offensive.” In Military Strategy and the Origins of the First World War: An International Security Reader, edited by Steven E. Miller, Sean M. Lynn-Jones, and Stephen Van Evera, 59-109. Princeton, NJ: Princeton University Press, 1991. ISBN: 9780691023496.
    Required
  • Turner, L. C. F. “The Russian Mobilization in 1914.” Journal of Contemporary History 3, no. 1 (January 1968): 252-68.
    Required
  • Hermann, David. The Arming of Europe and the Making of the First World War. Princeton, NJ: Princeton University Press, 1996, pp. 199-224. ISBN: 9780691033747.
    Required
  • Fuller, J. F. C. “The Battles of the Marne and Tannenberg, 1914.” In A Military History of the Western World. New York, NY: Da Capo Press, 1956, pp. 182-228.
    Required
  • Lupfer, Timothy. “The Dynamics of Doctrine: The Changes in German Tactical Doctrine During the First World War.” Leavenworth Paper, no. 4 (July 1981): 69.
    Required
  • Keegan, John. “The Somme.” In The Face of Battle. New York, NY: Penguin Books, 1983 (reprint edition), pp. 204-84. ISBN: 9780140048971.
    Required
  • Weinberg, Gerhard L. “From One War to Another.” In A World At Arms: A Global History of World War II. Cambridge and New York, NY: Cambridge University Press, 1994, pp. 6-47. ISBN: 9780521443173.
    Required
  • Schweller, Randall L. “An Assessment of the International Distribution of Power (circa 1938-1940).” In Deadly Imbalances: Tripolarity and Hitler’s Strategy of World Conquest. New York, NY: Columbia University Press, 1998, pp. 203-208 (Appendix). ISBN: 9780231110730.
    Required
  • Young, Robert. In Command of France: French Foreign Policy and Military Planning, 1933-1940. Cambridge, MA: Harvard University Press, 1978, pp. 1-33. ISBN: 9780674445369.
    Required
  • Posen, Barry R. The Sources of Military Doctrine . Ithaca, NY: Cornell University Press, 1986. ISBN: 9780801494277.
    Required
  • Mearsheimer, John J. Conventional Deterrence . Ithaca, NY: Cornell University Press, 1983. ISBN: 9780801415692.
    Required
  • Herwig, Holger. “Clio Deceived.” In Military Strategy and the Origins of the First World War: An International Security Reader, edited by Steven E. Miller, Sean M. Lynn-Jones, and Stephen Van Evera, 262-301. Princeton, NJ: Princeton University Press, 1991. ISBN: 9780691023496.
    Required
  • Posen, Barry R. “Competing Images of the Soviet Union.” World Politics 39, no. 4 (July 1987): 579-97.
    Required
  • May, Ernest R. Strange Victory: Hitler’s Conquest of France . New York, NY: Hill and Wang, 2000. ISBN: 9780809089062.
    Required
  • Overy, R. J., and Andrew Wheatcroft. “The Soviet Union.” Chapter 5 in The Road To War . Revised and updated edition. London, UK: Penguin, 2000, pp. 210-257. ISBN: 9780140285307.
    Required
  • Kennedy, Paul. The Rise and Fall of the Great Powers . New York, NY: Vintage Press, 1989. ISBN: 9780679720195.
    Recommended
  • Mearsheimer, John J. Liddell Hart and the Weight of History . Ithaca, NY: Cornell University Press, 1989. ISBN: 9780801420894.
    Recommended
  • McNeill, William H. The Pursuit of Power . Chicago, IL: University of Chicago Press, 1984. ISBN: 9780226561585.
    Recommended
  • Rich, Norman. Hitler’s War Aims: Ideology, the Nazi State, and the Course of Expansion. New York, NY: W.W. Norton & Company, 1973, pp. xix-xxx. ISBN: 9780393054545.
    Recommended
  • Levy, J. “Preferences, Constraints, and Choices in July 1914.” In Military Strategy and the Origins of the First World War: An International Security Reader, edited by Steven E. Miller, Sean M. Lynn-Jones, and Stephen Van Evera, 226-62. Princeton, NJ: Princeton University Press, 1991. ISBN: 9780691023496.
    Recommended
  • May, Ernest R. “The U-Boat Campaign.” In The Use of Force: International Politics and Foreign Policy, edited by Robert J. Art and Kenneth Neal Waltz, 298-315. Boston, MA: Little, Brown, 1971.
    Recommended
  • Steiner, Zara. Britain and the Origins of the First World War. London, UK: Macmillan, 1977. ISBN: 9780333154274.
    Recommended
  • Berghahn, V. R. Germany and the Approach of War in 1914. London, UK: Macmillan, 1973. ISBN: 9780333106969.
    Recommended
  • Keiger, John F. V. France and the Origins of the First World War. London, UK: Macmillan, 1983. ISBN: 9780333285527.
    Recommended
  • Lieven, D. C. B. Russia and the Origins of the First World War. New York, NY: St. Martin’s Press, 1983. ISBN: 9780312696115.
    Recommended
  • Williamson, Samuel. Austria-Hungary and the Origins of the First World War. London, UK: Macmillan, 1991. ISBN: 0333420810.
    Recommended
  • Shanafelt, Gary. The Secret Enemy: Austria-Hungary and the German Alliance, 1914-1918. New York, NY: Columbia University Press, 1985. ISBN: 9780880330800.
    Recommended
  • Ropp, Theodore. War in the Modern World . Baltimore, MD: Johns Hopkins University Press, 2000. ISBN: 9780801864452.
    Recommended
  • Snyder, Jack. Myths of Empire . Ithaca, NY: Cornell University Press, 1993. ISBN: 9780801497643.
    Recommended
  • Weigley, Russell. The American Way of War . Bloomington, IN: Indiana University Press, 1977. ISBN: 9780253280299.
    Recommended

Prerequisites & course information

Prereq: Permission of instructor Acad Year 2027-2028: Not offered Acad Year 2028-2029: G (Spring) 3-0-9 units

Sources