THE tides of eastern Ukraine's war have shifted again. After weeks of ceding territory, the Ukrainian rebels have dealt government forces a series of swift counterstrikes. Backed by reinforcements from Russia, the separatists retook several towns near the regional capitals of Donetsk and Luhansk over the past week, and have opened up a third front to the south. The message was clear: we aren't going anywhere. The pro-Western Ukrainian government in Kiev has long asserted that the insurgency is a Russian creation. Despite moving more than 1,000 Russian troops into Ukrainian territory over the past week, the Kremlin calls the war a purely “domestic matter”, insisting that any Russians that happen to be found fighting are simply “volunteers” or soldiers on holiday. So who exactly are the rebels? After Ukraine’s president Viktor Yanukovych was ousted in February and Russia annexed Crimea in March, a patchwork of poorly coordinated militias began seizing government buildings throughout the Donetsk and Luhansk regions in April. These groups, who were made up almost entirely of disgruntled locals and sympathisers from elsewhere in Ukraine, declared independence in May as the Donetsk People's Republic and the Luhansk People's Republic. Together, this budding statelet calls itself “Novorossiya” (New Russia)—a revived term for southern Ukrainian territory conquered by the Russian empire in the 18th century. Eastern Ukraine has since attracted a number of shadowy Muscovites, some with ties to Russia's security services, who have transformed the ragtag movement. Igor Girkin (aka “Strelkov”) took control of the Donetsk military wing; while Alexander Borodai was appointed as Donetsk’s prime minister. They returned to Russia in mid-August after being replaced by Ukrainians in an apparent attempt to give Novorossiya a façade of local control.

The Donetsk and Luhansk People's Republics maintain separate administrations, complete with their own prime ministers and cabinets (including separate defence ministers). The Luhansk region, which borders Russia, has served as the primary conduit for arms and fighters, while the Donetsk region further west has borne the brunt of the Ukrainian offensive. They retain operational independence on their territories, but coordinate closely. Throughout the summer, as weapons and fighters flowed across the porous border, the separatist army has solidified into a formidable fighting force, one that bears little resemblance to its initial incarnation. It now possesses sophisticated weapons, including scores of tanks, artillery systems, armoured personnel carriers and anti-aircraft missiles, like the SA-11 "BUK" believed to have downed a Malaysia Airlines aeroplane in July—a tragically reckless act that the rebels still deny a hand in.

Although Vladimir Putin’s denials of Russian troop presence are farcical, the true extent of Russian involvement remains unclear. A full-scale invasion would probably include more than a few thousand troops—NATO officials say as many as 20,000 troops are poised at the border. For now, Mr Putin appears determined not to bear responsibility for a war that has killed nearly 2,600 people, most of them civilians. He continues to funnel his fighters and weapons to the rebel army in an effort to create a frozen conflict as he has done elsewhere, in the hope that he can one day insert “Novorossiya" into his new map of the world.

Dig deeper:

The evidence of Russian incursions into eastern Ukraine becomes even clearer (August 30th 2014)

NATO is responding better to Russian aggression in Ukraine, but there is more to do (August 30th 2014)

Flight MH17: "This is not a disaster. It is hell" (July 18th 2014)