No competent adult would write a blank check allowing the recipient to fill in the amount. Blank checks in the affairs of nations are another matter. On July 5, 1914, German Kaiser Wilhelm II issued such a check to his ally Austria and gave the world a metaphor that sums up the surrender of one nation to the caprices of another. That blank check was issued to an envoy of the Austro-Hungarian Empire who had come to Berlin after the assassination of Archduke Franz Ferdinand to inform the Kaiser that an unspecified ultimatum would be delivered to the Serbian government. What if Germany had read the ultimatum before Austria sent it? What if Tsar Nicholas II of Russia had restrained Serbia’s rejection of the ultimatum and negotiated with Austria? What if he, too, had not issued a blank check to his ally?

As the hundredth anniversary of the outbreak of World War I approaches, these what-ifs plague efforts to understand how war could have broken out when most European leaders and thinkers thought war unnecessary and unlikely. The English saw the assassination as one more skirmish in the long-running Balkan imbroglio. European nobility regarded the archduke’s anniversary visit to Sarajevo with his commoner wife as a vanity tour. Neither the French nor the English military were prepared for war, nor, as it turned out, were the Russian or Austrian armies. The short war that everyone anticipated dragged on for four dreadful years.

Would Kaiser Wilhelm have issued his blank check had he foreseen the consequences? He had an impulsive and paranoid character, seeing enemies on every border. Tsar Nicholas, cautious and weak-willed, had a fatalistic attitude, fearing war would end his regime. Neither emperor had significant curbs placed on their decisions, which were often made on the spur of the moment. Nor, expecting that war would be over in weeks, did either ruler have a strategy for the military stalemate they were plunging into. Austria and Serbia cashed their blank checks and World War I began.

Historians totting up the causes of the war are still puzzled by such reckless decisions, which resulted in the deaths of more than 16 million soldiers and civilians, brought down the German, Austro-Hungarian, Russian, and Ottoman Empires, and rippled disastrously through the twentieth century. All for a dead archduke?

In spite of the dramatic historical lesson, blank checks remain the currency of allied nations. During the twentieth century, seemingly competent leaders—most with far more restraints on their decision-making powers than the Kaiser or Tsar—went on issuing blank checks. Most recently, President George W. Bush gave the postinvasion government of Iraq a blank check and was prepared to stand by indefinitely while it got its house in order; it never did. President Barack Obama finally canceled the check. The United States stands in supplication behind the teller’s window as Obama tries to cancel the U.S. check held by Afghan President Hamid Karzai. For the past twenty years, the United States has given Israel a blank check in its occupation of the West Bank and attacks on Lebanon and Gaza. More recently, it appears that Israel’s threat to attack Iran has been backed by the full faith and credit of the United States.

In November, Obama and Secretary of State John Kerry opened negotiations to ratchet down Iran’s nuclear program. Israeli Prime Minister Benjamin Netanyahu reacted as if a hold had been put on Israel’s check. In December, twenty-six U.S. senators, including several Democrats, introduced the “Nuclear Weapon Free Iran Act of 2013,” calling for ever more sanctions on Iran and requiring that it surrender all of its nuclear facilities and materials. The senators are clearly willing to derail negotiations, and while they were at it, they included this provision in the bill: “If the government of Israel is compelled to take military action in legitimate self-defense against Iran’s nuclear weapon program, the United States government should stand with Israel and provide, in accordance with the law of the United States and the constitutional responsibility of Congress to authorize the use of military force, diplomatic, military, and economic support to the government of Israel in its defense of its territory, people, and existence.”

Read that carefully, as Netanyahu and company assuredly do. Would they be mistaken in concluding that they can fill in the blank whenever they choose, whatever the amount—and the United States will pay? True, Israel faces threats from Iran and other neighbors, but a blank check from the United States will not help Israel and the greater cause of peace any more than the blank checks of 1914 served those who issued or received them.