In the last two weeks, Russia has conducted several waves of strikes against Ukrainian ports on the Danube River using Iranian-produced one-way attack uncrewed aerial vehicles (OWA UAVs). It is highly likely attempting to coerce international shipping into stopping trading via the ports.
OWA UAVs have struck targets as close as 200 metres from the Romanian border, suggesting that Russia has evolved its risk appetite for conducting strikes near NATO territory.
There is a realistic possibility that Russia is using OWA UAVs to strike this area in the belief they are less likely to risk escalation than cruise missiles: Russia likely considers them as acceptably accurate, and they have much smaller warheads than cruise missiles.
