Last week, Hillary Clinton made history by becoming the first presumptive female nominee for president of a major U.S. political party. In doing so, she fended off a serious threat from Vermont Sen. Bernie Sanders, a self-proclaimed socialist who has become a titanic force in the Democratic Party.

Sanders has challenged Democratic orthodoxy on free trade, Mideast policy and the scope of executive power to conduct unlimited military campaigns under the auspices of the war against terrorism. In doing so he has exposed one of Clinton's greatest vulnerabilities in a general election: Her judgment in conducting foreign affairs.

Clinton's record as a military hawk is well-known. She voted for the Iraq War as a senator. As secretary of state, she pushed for U.S. intervention in Libya and lobbied President Barack Obama to take military action against Bashar Assad in Syria. She was lukewarm about the nuclear deal with Iran. With respect to Israel, in March she gave a major policy speech to the American Israel Public Affairs Committee without so much as mentioning the plight of the Palestinians — a point later highlighted by Sanders, a son of Jewish immigrants, during their debate in Brooklyn.