Ukrainian businessman Volodymyr Ryabov has decided to improvise his own checkpoint between the Russian border and his home town of Luhansk in eastern Ukraine. He’s pulled concrete blocks from the foundation of his half-built house and turned them into roadblocks. He fashioned a homemade boundary sign warning: “Attention! State border of Ukraine. No trespassing!” He even dug an anti-tank ditch, and set up one of the rooms in the house to feed border guards. The Ukrainian press has hailed him as a model for those free citizens of a free country “who do not expect help from the state” and are ready to defend the nation themselves.

But the biggest threat to Ukraine at this moment is not coming so much from Russian tanks as from Russian “tourists,” some of whom, of course, are not tourists at all.

Over the last ten days, the unrest in east Ukraine has intensified dramatically as armed men continue to mount a concerted campaign to seize government buildings. The banners of today’s Russia, and of the historical Soviet and Russian empires, have been raised high alongside those of newly declared “independent” regional republics. The attacks hit Luhansk, Kharkiv, and Donetsk last weekend, Sloviansk, Kramatorsk and Druzhkovka this weekend. Despite widespread reports that these people belong to Russian special forces, they usually tell reporters they are just resentful local citizens, part of a supposedly represssed Russian-speaking minority.

The government in Kiev has hesitated to respond with force out of fear that bloodshed will give Russian President Vladimir Putin the excuse he’s looking for to mount an open invasion. But on Sunday morning Ukrainian Interior Minister Arsen Avakov announced operations were under way to retake the police station in Sloviansk.

On Saturday, U.S. Secretary of State John Kerry made a very blunt phone call to Russian Foreign Minister Sergei Lavrov, expressing “strong concern that attacks today by armed militants in eastern Ukraine were orchestrated and synchronized,” as they were in Crimea in the prelude to its annexation by Moscow. “Militants were equipped with specialized Russian weapons and the same uniforms as those worn by the Russian forces that invaded Crimea,” according to the State Department readout of the Kerry-Lavrov phone call. “The Secretary made clear that if Russia did not take steps to de-escalate in eastern Ukraine and move its troops back from Ukraine’s border, there would be additional consequences.”

But the Russian game today, like the “Great Game” the tsars played for two centuries against the British Empire, is a complicated blend of covert action, economic warfare, propaganda and the threat of outright combat. If Putin’s strategy works he will be able to reassert control over much or all of Ukraine and perhaps move on to other former territories of Moscow’s past empires as well.

One of the Kremlin’s key tactics is to obscure the origins of those forces spearheading its operation in east Ukraine, and one of the ways it’s doing that is to promote what might be called insurrectional tourism.

“Russian Spring,” as it turns out, is not only a revanchist motto out of Moscow, which we started hearing before the Crimea annexation, it’s a website, too. Adventure seekers who dream about reviving the U.S.S.R. can go online to share information about how to travel to Ukraine and, well, make a terrible mess there. Before their departure soldiers of fortune are advised to familiarize themselves with the slogan, “Leave for the front! Glory to Russia!” along with rules of behavior for a Russian tourist who wishes to get to “the territory of brotherly Ukraine”:

“From the beginning of the Crimea events on March 2 until the present time Ukraine has refused entry to more than 10,000 Russians and the figure is growing every day,” cautions the advisory. “The situation is created artificially to reduce the quantity of people who could be involved in the conflict on the side of Russian-speaking Ukrainians.”

So, as the “Russian Spring” site recommends, “you should comply with certain rules” and know certain facts. Here is a somewhat abbreviated but informative checklist that suggests, among other things, the kinds of “tourists” likely to be crossing the border:

1. Ukrainian border guards are loyal to Kiev, which has given them the order to look for any reason to refuse entry to people with Russian passports.

2. “Even if you have just one camouflaged T-shirt, some pepper spray or a knife you could be deported back to Russia as a commando. So if you need these things you can purchase them in Ukrainian shops: the prices are not higher than Russians ones.”

3. “We advise you not to publish anti-Bandera [that is, anti-Ukrainian] propaganda on your social network accounts.”

4. “Remember that your mobiles can have undesirable photos such as military patriotic events with your participation. Don't save SMS texts like, ‘Left for front, glory to Russia!’ and similar ones.

Among the most often cited reasons for refusing Russians entry into Ukraine, according to the web site’s checklist, are:

1. Lack of the required $600 in cash guaranteeing financial support.

2. Inability to confirm the purpose of the visit to Ukraine or the precise destination.

3. Subject has military bearing, short haircut, brought a military uniform or wears the Cossack chevron insignia.

4. Subject has the certificate of a combat veteran.

5. Subject has athletic build, calloused knuckles, broken nose – characteristics of martial arts practitioners.

6. Subject has “Airborne Troops” tattoo or similar.

7. Border guards discover that subject is a reserve officer of the Russian Federation navy.

8. There is a message on subject’s mobile such as, “Left for Crimea, from there to the front to fight, if something comes up, say I am ill.”

The incriminating items most often founded by Ukrainian border guards, according to “Russian Spring,” are: military belts, blackjacks, binoculars, Russian flags, combat knives, military certificate of a squad leader of airborne troops or other special units.

But, obviously, Kiev’s border security policy isn’t working all that well.

A journalist from Russia’s Moskva FM Radio broadcasting from Donetsk asked a local rebel commander, "Can you tell me your name?" He answered: "Of course, I am Paramonov Pavel Vladimirovytch.”

"Are you from Donetsk?"

"Of course not. I am from Yefremov, Tula region [Russia]."

"What are you doing in Donetsk?"

“I am helping brotherly people to defend their rights, do you have another questions?"