It's happening, page-21

https://foreignpolicy.com/2020/10/14/ai-drones-swarms-killer-robots-partial-ban-on-autonomous-weapons-would-make-everyone-safer/

In 2018, a group calling itself the Free Alawites Movement claimed responsibility for launching 13 drones made largely of plywood, duct tape, and lawnmower engines that attacked Russia’s Khmeimim Air Base in Syria.The movement claimed the successful destruction of a $300 million S-400 surface-to-air missile system.
Russian officials acknowledged the drones flew autonomously and were preprogrammed to drop bombs on the base but claim no damage was done. However, in Libya, Turkish Bayraktar TB2 drones disabled at least nine Russian air defense systems. The Bayraktar drones are considerably more advanced than those used in Syria, but they illustrate the same principle: Drones pose major threats to air defenses and other expensive systems.
An adversary could fling tons of drones against a $1.8 billion USS Arleigh Burke-class guided-missile destroyer in an attempt to disable or destroy it and still have a cost advantage. Facing such a threat, great powers should choose to lead—rather than resist—the arms control charge for certain weapons. Yes, great powers would give up the potential to unleash their own massive swarms, but swarms are likely to favor weaker powers. If swarms are most effective when used en masse against big, expensive platforms, then major powers that possess such expensive equipment stand to lose the most. Swarms might also be easier to control.