In the last two days, Russian troops have attempted to relieve pressure on their separatist allies in Donetsk and Luhansk by opening what amounts to a third front south of the two breakaway cities. On Wednesday, Ukrainian troops, who had been steadily advancing on separatist forces in the east, beat a hasty retreat from Novoazovsk, where they were routed by troops and armor streaming across the Russian border. Novoazovsk lies a mere 20 miles from the southeastern port city of Mariupol, a city of 500,000.

Will Putin continue the advance past Mariupol, toward Crimea — which he annexed in March — and potentially all the way to the breakaway region of Transnistria in Moldova? Or is this a mere tactic to ensure the survival of Putin’s proxies in Donetsk and Luhansk?

Russia has been involved both politically and militarily in the armed uprising in Ukraine since it began in April but recent developments mark a sharp escalation in the five-month war. Russian troops are now openly fighting on Ukrainian soil, even as Moscow continues denying that it has mounted what can only be called an invasion of its neighbor.