For months, Ukraine has picked off Russian soldiers by the thousand around the front-line city of Pokrovsk, using small drones armed with bombs to tie down a numerically superior force.

Now though, Russian troops are creeping forward in a summer offensive that has probed weak spots in Ukraine’s defenses and last week saw some Russian soldiers enter the city for the first time, according to geolocated footage on Ukrainian and Russian Telegram channels.

Ukrainian soldiers’ success in stopping their enemy from taking Pokrovsk since last year has long thwarted one of Moscow’s central military goals, although the city itself is heavily damaged and all but a few hundred of the 60,000-strong population has fled.