Ukraine war drone attacks 'waking up' world's militaries
This week has seen Russia use waves of Iranian-built Kamikaze drones to attack Ukrainian cities, with the West sending its latest air defence systems to Kyiv to try and combat them.
Both sides have used unmanned aerial vehicles (UAVS) during the war.
Drone expert David Hambling told Forces News the conflict in Ukraine "is far and away the largest scale use" of drones ever seen in warfare.
Watch: Ukrainian police officers fire at drones in Kyiv.
"The genie is well and truly out of the bottle now and you do feel the world is suddenly waking up to the fact that if your military hasn't got lots of drones, they're going to be at a massive disadvantage against anyone who does," he said.
The Russians are thought to be using Iranian-built Shahed-136 drones.
Iran has denied it's supplying UAVs to Moscow, but Tehran's track record would indicate otherwise and the US State Department says the Iranians are also training Russian drone pilots.
A "relatively small number" of personnel have been sent by Iran to Crimea, to assist Russian troops in launching Iranian-made drones against Ukraine, according to National Security Council spokesman John Kirby.
"The information we have is that the Iranians have put trainers and tech support in Crimea, but it's the Russians who are doing the piloting," Mr Kirby said.
Mr Hambling told Forces News the Shahed drone is "a very cheap, very basic bit of kit".
"But that is its massive strength because it is cheap, it can be launched in very large numbers," he said.
"According to the Ukrainians, the Russians have bought more than 2,000 of them off Iran."
Ukraine has been given various air defence systems to try to down incoming drones and missiles, but some have simply been shot down by soldiers with rifles.