When U.S. President Joe Biden declared Friday he was convinced President Vladimir Putin of Russia had decided to attack Ukraine "in the coming week, in the coming days,” the skeptics among American allies suddenly fell quiet. Hours before, Biden had informed them that U.S. intelligence agencies had just learned that the Kremlin had given the order for Russian military units to proceed with an invasion.

Now the debate has shifted to how Putin will do it: in one massive nationwide attack; a series of bites that dismantle the country, piece by piece; or a pythonlike squeeze. That last option is made all the easier with the news Sunday morning that Belarus is allowing Russian troops to remain indefinitely, where they can menace Kyiv, the Ukrainian capital. Putin might be betting that he can shatter Ukraine’s economy and oust its government without having to immediately roll in tanks.

Putin’s strategic choices over the next few weeks may make a huge difference in how the world reacts.