If they ever really left in the first place, the Russians are back in eastern Ukraine. Just days after rebels declared independence after a Moscow-backed plebescite, heavy weapons and tanks from the Russian army rolled back into Luhansk, and another column entered the region from another unspecified crossing point, AFP reports from sources within the Ukrainian military

A column of 32 tanks and other heavy weapons has entered Ukraine from Russia, the Ukrainian military said Friday, after the latest fighting left five dead and at least 31 injured. …

Another column including trucks and three mobile radar stations crossed another border point in the same region, he said.

CNN interviewed Ukraine’s ambassador to the UN on Monday after the plebescite, which Ukraine strenuously protested and declared illegitimate. Yuriy Segeyev predicted that this would become “Crimea two”:

The vote for autonomy in Ukraine’s rebel-held provinces of Donetsk and Luhansk is a repeat of Russia’s annexation of Crimea, the Ukrainian Ambassador to the U.N. Yuriy Sergeyev told CNN’s Christiane Amanpour on Monday.

“This is Crimea two,” Sergeyev said, adding that Russia annexing the eastern provinces is one of the “possible scenarios.”

Voters went to the polls on Sunday to elect leaders to rule the self-proclaimed Donetsk and Luhansk republics. The election was backed by the Kremlin, but labelled by Kiev and several Western governments as illegitimate, echoing what happened in the Crimean peninsula before Russia annexed it in February.

Ukraine is facing an “artificial scenario when alleged leaders backed by alleged support – they will propose, can propose to be a part of Russia,” Sergeyev said.

He also expressed concern that the fragile ceasefire agreed between Kiev and pro-Russian rebels in Minsk, Belarus, in September, has now been compromised.

This move is directly out of the Crimea playbook. In that seizure, Russian troops infiltrated the peninsula in uniforms without insignia, seized control of the region, and then held a plebescite on annexation to the country that had occupied their land. Immediately afterward, Russia invested Crimea militarily, this time openly, and secured its new possession. This is exactly what has unfolded in Donetsk and Luhansk, just over a longer period of time.

Amanpour cuts to the heart of the question for the West now that Russia has re-invaded in force. It’s the classic fait accompli challenge: what is the world to do when an aggressor nation simply takes what it wants in defiance of the international community, especially on the arguable basis of self-determination with the phony plebescite? It’s always a bit dangerous to reference analogous actions from the 1930s, but this was also the way Adolf Hitler expanded German reach, with the Austrian Anschluss and the seizure of Czechoslovakia despite Western security assurances to both nations. At the time, the West demurred from action by consoling themselves that Hitler really only wanted a return of traditionally German territory to his Reich. Perhaps that thought will be comforting for a time with Vladimir Putin and Russia, too.