Nearly three years after President Vladimir Putin invaded Ukraine, his troops are making steady progress on the battlefield.

That will take some doing. Putin remains uninterested in peace talks as long as Russian troops continue to gain ground in Ukraine’s east, albeit at a slow pace, and while Ukrainian forces hold seized territory in the Kursk region inside Russia, according to John Herbst, a former U.S. ambassador to Ukraine, and other former officials.

President Trump jabs at the Russian leader with threats; Vladimir Putin responds with flattery. But there are notable signals in their jousting, including a revived discussion about nuclear arms control.