Russian President Vladimir Putin chairs a meeting with permanent members of the Russian Security Council at the Novo-Ogaryovo residence outside Moscow on October 6, 2014. (Michael Klimentyev/AFP/Getty Images)

A MONTH after a cease-fire was declared in eastern Ukraine, the fighting continues: 75 Ukrainian soldiers and civilians have died since Sept. 5, the government says. Russian-backed forces have been expanding the territory essentially ceded to them by the Ukrainian government after its army was routed by invading Russian troops. The Donetsk airport, held by the government, remains under siege; if Russian forces capture it, their enclave will have another supply route outside Ukrainian control.

As it is, what is variously called the “Donetsk People’s Republic” or “Novorossiya” is rapidly acquiring the accouterments of other territories Moscow has seized inside eastern European countries. Ignoring Ukrainian legislation calling for local elections, Russia’s puppets have established a “supreme Soviet,” like that of the former Soviet Union, as well as a secret police force called the MGB — like the Soviet KGB. According to the New York Times, military tribunals have imprisoned about 1,000 people. A “deputy defense minister” told the newspaper that the system of government being constructed was “military Communism.”

European Union diplomats are still working to set up a proposed buffer zone between Ukrainian and Russian forces. But many already are expressing relief that their frequently announced objective — “deescalation” — seems to be in reach. By that, they mean that Russian President Vladi­mir Putin does not appear to be aiming, for now, at sending his forces to capture new cities in eastern Ukraine or to establish a land corridor from Donetsk to occupied Crimea.

Yet Mr. Putin is on the cusp of achieving all his major objectives. In addition to Crimea, he has captured a strategic slice of territory containing up to 10 percent of Ukraine’s population, creating a “frozen conflict” that he can use to keep the rest of the country permanently destabilized. He has bluffed Ukrainian President Petro Poroshenko and the European Union into postponing the implementation of an economic-association agreement that was the original cause of the conflict. He has pushed Ukraine’s economy into a free fall likely to intensify this winter, especially if Moscow fails to deliver supplies of gas or purchase Ukraine’s goods. If the Kiev government manages to hold successful elections this month and begins to find its footing, Mr. Putin can use his Donetsk clients to restart the war whenever he wishes.

In the meantime, the Kremlin hopes that its “deescalation” will induce the European Union and United States to lift the economic sanctions they stepped up last month. To her credit, German Chancellor Angela Merkel, a crucial voice in any such decision, said last week that the union was “very far away [from] consideration to take back sanctions.” However, neither E.U. leaders nor the Obama administration have spelled out what conditions Moscow must meet to win a respite.

That opens the door to letting Mr. Putin off the hook before he takes steps that are essential to preserving what remains of Ukraine’s sovereignty. These include withdrawing all Russian forces and military equipment from Ukraine and sealing the border between the countries, with monitoring by international observers. Ms. Merkel and President Obama should insist on these terms and make them public. Otherwise Mr. Putin will be encouraged to renew the aggression that already has proved fruitful for him.