While the world was caught off guard by Mr. Putin’s sudden peace offensive, analysts in Moscow cited several robust military, economic and political reasons he might be inclined to switch tracks.

First, there has been an increasing sense here, as elsewhere, that conditions in Ukraine were rapidly approaching the situation in Yugoslavia in 1991, when that country broke into pieces. The violence among various factions was creating facts on the ground, they said, that nobody could predict or manage.

Paradoxically, some added, this dynamic was nurtured in large part by round-the-clock reports on Russian state television that Ukraine was heaving with violence instigated primarily by neo-fascist cells emanating from western Ukraine. But with the notable exception of some 40 deaths in riots last week in Odessa, far from the separatist hotbeds of Slovyansk and Donetsk, the violence was mostly confined to small skirmishes.

There were worrying signs that was changing, however.

“The problem is that in all these types of conflicts, once the black swans have started to fly, you will never control the situation,” said Sergei A. Karaganov, dean of the School of International Economics and Foreign Affairs at the Higher School of Economics in Moscow and a periodic adviser to the Kremlin on foreign policy.

In modern international relations and finance, “black swans” refer to random, unexpected events with unforeseeable consequences. “Law and order was beginning to fall apart, and more and more groups were fighting each other,” Mr. Karaganov said.

The other reasons follow a certain logic. Mr. Putin wants to shape Ukraine’s future, but an invasion of Ukraine by the Russian Army would be wildly expensive, bloody and unpredictable. Even a nominally successful invasion could breed an insurgency in the east by pro-Ukrainian militants, while the partition of the country would stick Russia with a failed state in southeast Ukraine that would take tens of billions to restructure. It would also create an implacably anti-Russian and pro-European state in western Ukraine that would most likely join NATO as fast as it could.