The tipping point was reached at the Geneva meeting this week that resulted in the Geneva Agreement. The critical issue was how much power would be devolved to the regional governments in the revised constitution.
The Ukranian delegation drew a line in the sand that they can ill-afford, given the unwillingness of the West to launch a war with Russia to protect Ukraine, and the unwillingness of many Ukranian soldiers to fire on other Ukranians.
The line that was drawn in the sand was this:
The most bellicose moments came when the Ukrainians and diplomats from the West raised the issue of Crimea -- or whenever the Ukrainians pushed back against Russian demands for political reforms that would serve Russian interests. “I am ready to inform the Russians about our ideas on a constitution or on how we will protect the rights of Russian speakers,” says Deshchytsia. “But I am not going to discuss details about reforms or accept that Moscow can insist on certain things being put into the text of the constitution or insist on particular local government changes.”
Whether they like it or not, the Kiev government will have to listen to the demands of Russia (whether they come directly from Russia or via Russia’s proxies in later talks on constitutional reform involving delegations from the regions). The reforms tabled to date by Kiev fall far short of meaningful delegation of powers to the regions, and will need to be substantially improved if Ukraine is not to end up in a civil war of east versus west.