South Vietnam and Iraq are different, of course: Washington used its military might to keep one artificially divided and the other artificially unified. But Saigon in 1975 and Baghdad in 2014 share a frailty born of dependence on American power. Both cracked like a hollow egg at their first real test. In March 1975, the loss of Hue and Danang foreshadowed a military rout that led to the collapse of the capital of Saigon only six weeks later. In Iraq the loss of Mosul and Tikrit brought ISIS almost to the gates of the capital, intensifying ethnic unrest in the city and threatening the future of Baghdad.

Both countries’ leaders appealed for American air power, to no avail. In March 1975, South Vietnam President Nguyen Van Thieu sent a detailed list of bombing targets to the White House and called upon private agreements made by former President Richard Nixon guaranteeing American military help. President Gerald Ford turned him down.

Similarly, Iraqi Prime Minister Nouri al-Maliki began public and private appeals for American air support after the fall of Mosul and Tikrit. President Obama has demanded substantial political reforms in Baghdad in exchange. Maliki’s reluctance to work with his political rivals resembles President Thieu’s refusal to widen his government or consider any accommodation of his political opponents. Thieu ultimately stepped down at U.S. urging and fled the country 10 days before it fell. Obama may leave another American ally to his fate.