An image from surveillance video provided by the U.S. military shows what they say is a drone being shot down over the Strait of Hormuz on Thursday. (Reuters)

Thursday, Iran shot down an important U.S. aerial surveillance asset, an RQ-4 Global Hawk, widely known as a drone, reportedly in international waters. Many observers have been concerned that, given the background, this could push the two nations toward war.

Here’s what you need to know about drones and military escalation as the possibility of a confrontation looms.

It’s easy to shoot down most current-generation drones.

Current-generation drones generally fly slowly and cannot defend themselves, making them vulnerable to enemy air defenses. Countries have not shied away from exploiting this vulnerability, as drone shoot-downs have become somewhat commonplace. For example, Indian forces have repeatedly fired at Pakistani drones, and Turkey shot down a Russian drone in the midst of the Syria conflict. Iran’s latest action is not unprecedented.

Drone shoot-downs usually don’t lead to military escalation.

While shooting down drones does generate publicity, it has not led to escalation. As we discussed in an article in International Security, one of the reasons countries use drones is to deploy military assets while reducing the risk to their own soldiers and limiting the prospects of escalation. Shooting down a drone does not generate the same level of public outrage as shooting down a pilot, so it generally does not galvanize the domestic case for war.

In fact, the use of drones has caused the opposite concern, that this so-called light footprint approach to war disconnects the public from costs of conflict and creates public apathy rather than accountability.

Thus, shooting down a drone, even when the countries involved are the United States and Iran, is unlikely to be a cause for war, though it certainly could raise tensions. This does not change the fundamentals that one of us, Michael Horowitz, and Elizabeth Saunders laid out here at TMC earlier in the week.

Is the Iran context different?

From a military perspective, shooting down an RQ-4 has some significance. It is a much more expensive intelligence, surveillance and reconnaissance asset than the more commonly known MQ-9 Reaper drone. Thus, Iran’s action is certainly costly to the U.S. military — but a lot less costly than if it had shot down an equivalent aircraft with U.S. military personnel aboard. Trump said as much this afternoon:

The other factor that could make this situation different is that U.S.-Iran tensions were already increasing. Still, previous drone shoot-downs suggest this one is unlikely, on its own, to generate new, significant pressure for escalation to war. In 2011, Iran allegedly used a spoofing technique — hacking the drone’s controls — to bring down a U.S. RQ-170 Sentinel drone and commandeer it into Iran, causing tensions but no notable escalation. In 2018, an Israeli Apache helicopter shot down an Iranian equivalent of the RQ-170 drone, a rare instance of direct military confrontation though against the backdrop of perennial diplomatic tensions. Still, the encounter did not escalate notably.

If this escalates, it’s not about the drones.

Countries go to war when they have decided it is in their interests to fight. Given the issues laid out above, shooting down an RQ-4 drone — even in international waters — should not fundamentally change the likelihood of escalation. So the drone shoot-down continues a pattern of rising tensions, but if this incident escalates into a larger military confrontation, it suggests the United States and Iran were already on the path to war for other reasons.

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Michael C. Horowitz (@mchorowitz) is professor of political science and the associate director of Perry World House at the University of Pennsylvania. He is the author ofThe Diffusion of Military Power” (Princeton University Press, 2010).

Sarah E. Kreps (@sekreps) is professor of government at Cornell University. Her most recent book is “Taxing Wars: The American Way of War Finance and the Decline of Democracy” (Oxford University Press, 2018).

Matthew Fuhrmann (@mcfuhrmann) is professor of political science at Texas A&M University. He is the co-author of “Nuclear Weapons and Coercive Diplomacy” (Cambridge University Press, 2017).