On the eve of his country’s 1982 invasion of Lebanon, Prime Minister Menachem Begin told his Cabinet: “Israel will not allow genocide to happen.” Elaborating to the US Ambassador at the time, Begin insisted “under no circumstances will Israel allow the Christians of Lebanon in the 80s to become the Jews of Europe in the 40s.” During the invasion itself, US Ambassador to the UN Jeanne Kirkpatrick tried to convince President Ronald Reagan and the National Security Council that “the Israeli victory in Lebanon represented the greatest strategic turnaround in the West since the fall of Vietnam.” Drawing on recently declassified material from Israeli and American archives, as well as interviews with policymakers from both countries who were involved in the war, my paper examines the ideological context and the political impact of the US-Israeli strategic relationship in fomenting and sustaining the 1982 war. I argue that the rhetoric of humanitarian intervention in Israel combined with a reassertion of Cold War geopolitics in the Reagan White House to draw both countries into the midst of the Lebanese civil war. My paper demonstrates how the silences around the invasion in Israeli, American and Lebanese scholarship have served to obscure its central role in Middle Eastern and international history as well as the continuities that inhere in more recent regional interventions.