ISTANBUL — When Russia dropped its bombshell announcement of a plan to bring “stabilization” and “assistance” to rebel-held Aleppo by emptying it of its inhabitants and its defenders, the U.S., the UN, and any number of countries working to end the war in Syria were taken aback.

Gen. Sergei Shoigu, the Russian defense minister, announced that President Vladimir Putin had issued a decree ordering a “large scale humanitarian operation” in Aleppo, which has been under siege for three weeks.

But there was no advance consultation on the decision to set up four corridors—three for civilians and one for armed combatants—to leave the city. Western diplomats said it amounted to imposing a military solution on Syria’s biggest metropolis as well as a violation of international law.

A top official of the Syrian opposition said he’s convinced Russia’s intent is use the methods it deployed to destroy Grozny. The capital of the Chechen Republic was the scene of bloody combat in 1994-95, and then again in 1999-2000, early in Putin’s first presidency. At that point leaflets were dropped offering people safe passage out of the city, and after a brief pause the real devastation began. In 2003, the United Nations reportedly called Grozny “the most destroyed city on earth.” The war was over, and on Putin’s terms.

Even the Obama administration, long accused by its critics of fecklessness and of appeasing the Assad regime’s two outside supporters, Iran and Russia, mustered a strong verbal response.

A State Department spokesman said the Russian operation appeared to be “a demand for the surrender of opposition groups” in violation of joint U.S.-Russian understandings and a UN Security Council resolution.

Secretary of State John Kerry has been involved in an intense diplomatic drive that involved major security concessions by Washington in hopes it would lead to an end to the fighting and the start of peace talks—then Russia sprang its plan last Thursday.

In several days of phone conversations with Moscow, Kerry was unable to obtain clarifications of how the new decision was compatible with the talks he’s been holding with his Russian counterpart, Sergei Lavrov.

European diplomats said Kerry’s current initiative, which involved a highly controversial concession to share intelligence with Russia and to conduct joint and coordinated attacks on Jabhat al-Nusra, could collapse in short order.

According to Assad’s political opponents, that is not the worst of it.

Syrians were not at the table Thursday when Russia unveiled its plan to the U.S., the UN, and more than a dozen other countries in talks on the cessation of hostilities, but the president of the Syrian Coalition of opposition groups, Anas Abdah, said he had been briefed by diplomats attending the meeting.

According to his information, Russia told the ISSG, the International Syria Support Group, that the Assad regime will spearhead a major offensive to take over the entire city. All combatants who choose not to leave “will be dealt with as Jabhat al Nusra,” the rebel force that—until it changed its name and ostensible affiliation a few days ago—was the al Qaeda branch in Syria.

By prior agreement between Russia and the U.S., any country can freely target the Islamic State extremists (ISIS) or Nusra on Syrian territory. In actual fact, Russia has repeatedly attacked U.S.-backed moderate rebels and civilians, claiming it was attacking Nusra.

This means that Russia will feel free to target any location in rebel Aleppo and level it, Abdah said.

“The Russians want to apply the example of Grozny to Aleppo,” he said. “There will be no red lines. Every hospital, every school, every civilian area, everything is targeted.”

Based on the briefing, Abdah sent an urgent message to rebel forces and civil authorities to prepare immediately for the offensive and if at all possible to try to withstand the offensive—at least until the end of September, and more likely until March 2017.

In an exclusive interview with The Daily Beast, Abdah said the timing of Russia’s new initiative almost certainly was geared to the U.S. election cycle, and that Russia wanted to present a fait accompli to the U.S. in the next two months.

After September, the U.S. administration will not be able to be a party to any major political agreement, and then the Russians “will have to wait until spring of next year, when the new administration takes office and formulates its policies,” he said.

The question is whether Aleppo residents, who are reported to have a maximum of six months of food supplies, can hold out that long.

Aleppo has been under siege since July 10, when Syrian government forces, aided by Russian air support, Iranian regular forces, Lebanese Hezbollah, along with Iraqi and Afghan militias, closed the Kastello road, the last supply route into the eastern part of the city.

“There will be direct consequences for civilians,” said Abdah. “We will try to protect civilians in the best possible way. We expect armed fighters from outside Aleppo will try to coordinate their work to break the siege and bring in the required humanitarian supplies,” he said.

Abdah said even if Russia and the Syrian government open corridors to regime-held western Aleppo, he doubted that Aleppo residents will flee the city in big numbers for an uncertain future in displaced persons’ camps or as destitute refugees in another country.

“So far the people of Aleppo have not shown any sign of succumbing to these attempts by the Russians,” he said. “Of course it’s up to them to decide whether they want to stay or leave. But we have observed that people would like to stay for the moment to defend their families, their properties and their life in the city.”

Echoing the bitterness of many Syrians, Abdah said the United States is playing a role that no one can understand.

“I feel the international community has abandoned us at this critical stage,” he said. “What the Russians are demanding is very clearly a war crime. I believe the U.S. could stop this. Russia would not do this without the implicit feeling that there will be no consequences.”