Feb 21st 2018, OSCE UAV (drone) flew over a military base near the town of Krasnyi Luch, in Ukraine’s Luhansk Oblast (province). Spotted several Russian Grad Rocket Systems.
Russian invasion forces first started creating a base here around April 2015. Google Earth images here show it in Sept 2016, with several hundred tanks, artillery, transport trucks, armoured fighting vehicles and Grad rocket launchers highlighted in yellow box.
Close to the border, the base is used as a transit hub for Russian units entering and exiting Ukraine. Satellite images show there’s always a large amount of combat vehicles stationed there, with this reserve unit being able to either advance further into Ukraine, or be used to stem any major, Ukrainian military attacks.