Russian forces are invading now because the rebels are losing Luhansk and Donetsk is encircled.
“Luhansk .... is encircled.”
It would seem that the OSCE disagrees with you, and per today’s report there are no UK troops for 25Km on a line from Stanytsia-Luhanska to Lugansk.
Spot report by the OSCE Special Monitoring Mission to Ukraine (SMM), 25 August 2014
http://us6.campaign-archive1.com/?u=b11aceda364f8f9afa6cadbbb&id=12695ff596&e=97d3b684f9