I've covered many wars, but the current conflict in eastern Ukraine has to be one of the weirdest.

To begin with, it's not really a war. Indeed, commentators have dubbed it everything from the "phony war" to the "war that never was".

So what then is actually going on in eastern Ukraine: a mass political protest, uprising, insurrection, the prelude to a Russian invasion?

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Any definition, of course, depends on who you ask. During my time in eastern Ukrainian towns such as Donetsk and Sloviansk recently, I heard different people call it all of these things. Since my return home though, the question I'm most often asked concerns where the crisis might be heading?

No-one would rule out that the growing suspicion, bitterness, violence and murky, manipulative diplomatic manoeuvres under way there may yet plunge the region into the abyss of war.

My instinct, however - for now at least - is that we can expect more of what is known as "maskirovka" or disguised warfare. In eastern Ukraine this is epitomised by the masked pro-Russian gunmen that we have seen on a daily basis since the crisis began.

Their role was highlighted yesterday when hundreds of pro-Russian militants seized the regional prosecutor's office in Donetsk. This, again, was maskirovka in action.

John R Schindler, a former US National Security Agency counterintelligence officer who is now an analyst and instructor at the US Naval War College, calls it a "special war", a term he first coined in a study last year.

Maskirovka, says Mr Schindler, is something Russia excels at and incorporates, "espionage, subversion, and even forms of terrorism to attain political ends without actually going to war in any conventional sense".

Quoted recently in The New York Times, the former spy says this covert strategy was evident during Russian operations to quell rebellious Chechnya back in 1994 when Russia sent in a column of armoured vehicles filled with Russian soldiers masquerading as pro-Moscow Chechens.

Since then maskirovka has come to be the tactic of choice in eastern Ukraine for Russian President Vladimir Putin, a former KGB officer whose closest advisers are still mostly from that same Soviet-era intelligence agency.

To put this another way, Russia is conducting a slow-motion invasion of eastern Ukraine. This comes without the obvious advance of conventional forces so often illustrated by Western analysts' maps of the region using sweeping arrows to indicate the mass movement of troops and tanks from specific Russian units.

In many respects Mr Putin has happily encouraged the West to see his actions in terms of this conventional template of war and used large-scale troop movements and exercises on the border with Ukraine to suggest the Russian army is about to roll over the frontier.

While it would be foolish to rule out such a scenario, for the moment at least, maskirovka is more than achieving Mr Putin's aims. Only if the Ukrainian government in Kiev chooses to beef up its resistance to pro-Russian separatists, might we see a much more concentrated use of Moscow's military muscle. That, however, looks increasingly unlikely. Even Ukraine's acting President, Olexander Turchynov, has admitted that his forces are "helpless" to ease the intensifying grip of pro-Russian militants.

Faced with this, the Ukrainian parliament is currently deliberating a referendum on the decentralisation of power, possibly to coincide with Ukraine's presidential elections set for May 25 (or the potential run-off in mid-June).

Moscow has previously said it would not recognise these elections, but a few days ago in an interview with Russian daily Gazeta.ru, Russian Deputy Foreign Minister Sergei Ryabkov hinted it could recognise the poll "depending on how they are held" - a possible reference to the inclusion of the referendum.

Put another way, the extent to which Ukraine follows through on the decentralisation issue could be crucial in shaping Russia's response in the immediate future.

Ultimately, Russia will continue to use forceful pressure, whether in the form of ties to armed groups in the east or the threat of all-out military intervention. Some analysts remain convinced though that Moscow's goals are simply focused on a long-term strategy of preventing Ukraine from escaping Russia's economic and military orbit. But the crucial question remains as to what measures the Kremlin is prepared to deploy to ensure that?

For now Kiev has its work cut out to prevent the unrest spreading and yesterday there was little sign of Ukrainian forces being able to do that in Donetsk.

Day by day the authorities in eastern Ukraine are faced with battling phantoms, shadowy men with masks and without insignia that might betray on whose political behalf they are stirring things up. We can expect to see a lot more of the maskirovka men in the weeks and months ahead.