Unmanned aircraft had been used for reconnaissance for decades; what changed in 2001 was that they were armed. General Atomics' MQ-1 Predator could be flown from thousands of kilometres away over a satellite link, stay aloft for hours, and fire on the target it was watching. After the September 11 attacks this capability spread quickly, becoming central to U.S. operations in Afghanistan, Pakistan, Yemen and Somalia.

The argument it produced is legal and moral rather than technical. The standing in international law of targeted killings carried out in countries not declared battlefields remains contested, and for years official casualty figures have diverged sharply from the counts of independent research organisations. The second question is the asymmetry of risk: does the threshold for using force fall for a state that can do so without exposing its own soldiers? Since the 2010s this has been one of the central problems of military ethics.

The technology soon spilled beyond the military. By the mid-2010s cheap multirotor craft had become standard in surveying, agriculture, search and rescue, and filmmaking, with airspace regulation struggling to keep pace. In the 2020s the wars in Nagorno-Karabakh and Ukraine demonstrated the effect of comparatively cheap unmanned aircraft against conventional armour — Turkey's exported Bayraktar TB2 being among the most discussed examples. The drone is no longer an advantage peculiar to large armies but a widely held capability.