Three leading Democratic presidential candidates recently endorsed a new policy regarding U.S. military aid to Israel: It should be conditioned on Israel embracing policies toward the Palestinians favored by American progressives.

At the J Street conference last week, Sen. Bernie Sanders (I., Vt.) demanded that Israel "fundamentally change" its approach to terrorist-controlled Gaza, adding, "I think it is fair to say that some [U.S. military aid to Israel] should go right now into humanitarian aid in Gaza." Israeli officials believe such moves would enable Hamas to import more weapons and lead to another war. South Bend, Ind., mayor Pete Buttigieg called for cutting aid if Israel annexes the West Bank, which Israel has no plans to do. Sen. Elizabeth Warren (D., Mass.) said military aid should be cut if Israel is "moving in the opposite direction" of the "two-state solution," which most progressives believe Israel is doing. None of the candidates announced demands on the Palestinians.

The statements show the extent to which anti-Israel sentiment has spread from progressive activists to the Democratic Party mainstream. The calls for aid cuts are at odds with the longstanding strategic rationale for military aid to Israel, which has never been intended to promote peace with the Palestinians or the two-state solution.

U.S. aid largely takes the form of a credit that Israel must spend in the U.S. market, buying aircraft and arms from American defense companies, and long predates the concept of a two-state solution or peace process. It is concerned with promoting the broader U.S. interest in regional peace and security.

From the 1940s through the 1973 Yom Kippur war, Israel fended for itself almost entirely without U.S. military aid. It was this absence of superpower backing that enticed Arab states to believe that small, vulnerable Israel could be defeated on the battlefield—that period was marked by state vs. state wars whose effects rippled outward from the Middle East and harmed the United States. These wars threatened to draw in Cold War rivals, and in 1973 the defeated Arab states imposed an oil embargo that damaged the U.S. economy.

The United States could have responded to Arab antagonism by following the European playbook and squeezed Israel for concessions. But American strategists realized the best way to stop the wars wasn't to make Israel feel less secure, but rather to make Israel less defeatable.

The U.S. military aid that started in earnest in the form of an emergency arms resupply during the 1973 war has been perhaps the single-most effective U.S. policy toward the Middle East in the past half-century. With America now in Israel's corner, the Arab states were compelled to abandon the fantasy of wiping the Jewish State off the map. That led to what had previously been unthinkable: Egypt signed a peace treaty with Israel in 1979, and Jordan followed in 1994.

Other benefits to the United States flowed from military aid to Israel: With the Jewish state now fielding advanced U.S. weaponry against Arab states, which were armed with inferior Soviet weapons, regional skirmishes were turned into devastating morale-killers for Moscow. In one air campaign in June 1982, Israeli-piloted F-15s and F-16s shot down 88 Syrian-piloted Soviet MiGs. Israel lost a single F-16. Battles like this clarified for the world which side was likely to prevail in the Cold War.

Today, Gulf Arab states are drawing closer to an increasingly powerful Israel, seeking protection from Iran—another way in which U.S. military aid, which maintains Israel's "qualitative military edge" in the region, is promoting American interests and decreasing the likelihood that the United States will be called upon to directly protect regional allies.

Warren, Sanders, and Buttigieg did not acknowledge this history, or these strategic benefits. Since the progressive activists of the Democratic Party view Israel largely through the lens of the Palestinians, it was only a matter of time before they began to demand that all aspects of the U.S.-Israel relationship be subordinated to the politics of that issue.