The upsurge in fighting in Ukraine, with Russian troops and equipment pouring across the border, is a sign that Russian President Vladimir Putin has decided to engage the West in a dangerous game of “chicken,” the goal of which is to show that the only result of Western pressure on Russia will be renewed slaughter.

Given the objectives of the two sides, a renewal of the fighting was probably inevitable. Russia has fought from the beginning to remove the government in Kiev and prevent Ukraine from acceding to the European Union...