The U.S. military presence in northeastern Syria goes largely unnoticed until something terrible happens, like an American losing his or her life in an attack.

That’s precisely what happened on Thursday. One U.S. contractor was killed and six other Americans were injured when an Iranian suicide drone rammed into their position at a coalition military base near Hasaka in northeastern Syria. The United States responded with airstrikes against Iranian targets inside Syria.

This isn’t the first time U.S.- and Iranian-supported militias have fired at each other. Far from it. Indeed, the sporadic combat between the two resembles a never-ending game of cat and mouse. This is at least the fifth time the Biden administration has taken military action against Iranian-linked groups. The most extensive round took place last August, when Apache attack helicopters and AC-130 gunships struck militia fighters in eastern Syria who were preparing to fire more rockets on U.S. positions. Days earlier, the U.S. had conducted another strike in eastern Syria after those same militias fired rockets toward a U.S. base near the Syria-Iraq border.

US BASE TARGETED AFTER BIDEN ORDERS STRIKES AGAINST FACILITIES USED BY IRGC AFFILIATES

The pattern here is easy to spot. The U.S. is betting that good old-fashioned deterrence will work against Iranian forces and aligned nonstate groups: Strike them hard enough, and they will eventually recognize that the costs of attacking Americans aren’t worth the supposed benefits.

The calculation, however, hasn’t worked.

It’s extremely difficult to deter nonstate organizations, which lack institutions, wealth, territory, or a government to protect. Heads of state are primarily concerned with maintaining their power and self-preservation, and they usually avoid actions that may undermine those two objectives. The militias operating in Syria don’t have to worry about such practicalities. The only real thing they have to worry about is whether their sponsors in Iran reduce or eliminate their financial and military support. But there is no evidence whatsoever that Tehran is thinking about doing so. Indeed, these militias provide the Iranians strategic depth, serve as useful proxies in Iraq and Syria, and can be called upon in the event of a wider confrontation with the Americans.

Therefore, the tit for tat will continue until one of two things happens: U.S. troops withdraw from Syria, or the militias themselves stand down and demobilize. Since neither will happen anytime soon, it’s only a matter of time before we read about the next round of firings. And then, it will be deja vu.

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Daniel DePetris (@DanDePetris) is a contributor to the Washington Examiner's Beltway Confidential blog. His opinions are his own.