The US military has held a large-scale experiment, inviting tech teams to storm a mock city with more than 250 drones and rucksack-sized rovers.
Unmanned vehicles with varying levels of autonomy swooped into Fort Campbell, Tennessee, a culmination of tests running since 2017.
Swarming this technology can offer huge advantages to troops who are hindered by tall buildings and a restricted line of sight in urban areas, sending intelligence back to commanders far removed from the area of operation.
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The sight of drones taking over entire residential areas raises some ethical concerns, although Professor Peter Lee, a drones expert from the University of Portsmouth, says the capability is still some way off being used in real situations in populated areas.
"What appears on screen is probably more impressive looking than what can be applied right now" in uncontrolled conditions, he explained.
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The Defense Advanced Research Projects Agency (DARPA), the US military's research and development unit, set up the tests in 2017 – this was the sixth and final experiment under the OFFensive Swarm-Enabled Tactics (OFFSET) programme.
Previous workouts had seen a focus on raids, and Prof Lee suggests drones swarmed in this way cause unique issues for defence systems.
However, sophisticated swarming goes beyond the likely capability of non-state individual threat groups that could target the West, such as Islamic State, the expert said.
Timothy Chung, the OFFSET manager in DARPA's Tactical Technology Office, said: "We have demonstrated in the field that these swarm capabilities are rapidly nearing availability for future operations, and the lessons learned from OFFSET will certainly contribute to future swarm advancements."