Donald Kagan (; May 1, 1932August 6, 2021) was a Lithuanian-born American historian and classicist at Yale University specializing in ancient Greece. He formerly taught in the Department of History at Cornell University. Kagan was considered among the foremost American scholars of Greek history and is notable for his four-volume history of the Peloponnesian War. Early life and education Kagan was born in Kuršėnai, Lithuania, on May 1, 1932. His father, Shmuel, died before Kagan turned two years old, and his mother, Leah (Benjamin), subsequently emigrated to the United States with Kagan and his sister. He grew up in the Brownsville section of Brooklyn. He attended Thomas Jefferson High School, where he played football, before becoming the first person in his family to go to college. He graduated from Brooklyn College in 1954, received a master's degree in classics from Brown University in 1955, and a Doctor of Philosophy in history from the Ohio State University in 1958. Academic career Once a liberal Democrat, Kagan changed his views around 1969. According to Jim Lobe, cited by Craig Unger, Kagan's turn away from liberalism occurred in 1969 when Cornell University was pressured into starting a Black Studies program by gun-wielding students who had seized the Willard Straight Hall. Kagan reflected, "watching administrators demonstrate all the courage of Neville Chamberlain had a great impact on me, and I became much more conservative." Afterwards, Kagan was one of the original signers of the 1997 Statement of Principles by the neoconservative think tank Project for the New American Century, co-founded by his son Robert. On the eve of the 2000 presidential elections, Kagan and his other son, Frederick, published While America Sleeps, a call to increase defense spending. Known for his prolific research on the Peloponnesian War; Kagan is also famous for his work On the Origins of War and the Preservation of Peace, a comparative history examining four major conflicts (the Peloponnesian War, World War I, the Second Punic War, and World War II) and one non-conflict (the Cuban Missile Crisis) with the purpose of identifying how and why wars do or do not begin. Remarking in 2015 on the work, Kagan summarized the causes of war by quoting Thucydides: "You know, Thucydides has this great insight. I wish I could get people to pay attention – he has one of his speakers at the beginning of the war say, 'Why do people