Things are changing quickly in the volatile Ukraine. A week ago, a the prospect of civil war would have seemed unthinkable, but after violence that killed at least 70 protesters, a number of key players and observers began openly invoking the possibility, including former President Leonid Kravchuk, senior Russian Duma members, the mayor of the Eastern city of Donetsk, the pro-Russian government of Crimea and Polish Prime Minister Donald Tusk.

On Friday, it appeared an agreement had been reached between the government and the protesters for early elections and a return to a more liberal constitution. But the deal is by no means a sure thing, and many factors make any truce seem fragile.

During the violent week, the opposition had seized government buildings, including police stations, army barracks and the local branch of the interior ministry, in the western city of Lviv, which was already slipping out of the government's control before this week's events, and footage has emerged of soldiers surrendering to protesters, though they may have been conscripts who were already supporters of the opposition. Lawmakers in the region say they will no longer take orders from the central government. Protesters have also reportedly blocked a crossing at the Polish border.

Volodymyr Fesenko, head of the Penta Political Analysis Center in Kiev, told the Associated Press, "The violent scenario is a tragic and irreversible decision. ... Western Ukraine may even declare its insubordination. Any attempt to restore order in western Ukraine by force will start a civil war."

This still seems like a pretty unlikely scenario, even after this week's tragic events. Ukrainians may be split almost down the middle on whether they support the protests, but few support the use of force against protesters. Also, despite the country's clear split between the Catholic, Ukrainian-speaking West and Orthodox, Russian-speaking East, support for the country's independence has actually increased over the years, even in the East. (Crimea, which is majority ethnic Russian, may be something of an outlier.) And while the general ideological sentiments of the two camps are clear, it also seems as though actual enthusiasm for President Viktor Yanukovych is fairly thin, even among government supporters, and the opposition's leadership is divided among three men - Vitali Klitschko, Oleh Tyahnybok and Arseniy Yatsenyuk - all of whom carry some fairly serious flaws as potential leaders of a long-term nationalist uprising.

While a Czechoslovakia-style, or worse, Yugoslavia-style split appears unlikely, it is clear that a Rubicon of some sort was crossed this week. This government has entirely lost legitimacy, probably permanently, with a large segment of the population. If the lastest agreement cannot hold, the country may be entering a revolutionary situation or a prelude to deepening Belarus-style autocratic rule. It is unlikely that either situation would resolve itself without more bloodshed.

Joshua Keating is a staff writer at Slate. He was previously an editor at Foreign Policy magazine.