"I used to think that a US attack on Iran was unlikely. The US military is, after all, very thinly stretched these days, confronted as it is with a far more assertive Chinese Navy in the Pacific and the South China Sea, with a quagmire in its war in Afghanistan, a civil war in Syria, fighting and instability in Yemen and Somalia, continuing unrest in Iraq, and of course a newly reassertive Russia. It also faces enormous budget pressure at home. Add to that a weakening US and global economy that could be thrown into severe crisis by the oil price shock that would surely accompany any active war between the US and Iran. And yet, the decision by the US to send more attack aircraft, troops and ships to the regions around Iran and to step up covert actions against Iran, including sending in drone aircraft like the one captured a few months ago by Iranian forces, massively increases the chance of something going terribly wrong and setting off just such a conflict."
Accidents Happen, But We Can’t Afford One in the Persian Gulf
See also, itchy trigger fingers.