Ukraine may launch an onslaught against Russia at any time. Here's what's in store

Ukraine is preparing for a spring counter-offensive, likely in the south, which will mark a pivotal moment in the conflict. Russian defenses have been built up in parts of southern Ukraine, with layers of anti-tank ditches, obstacles, minefields and trenches. The challenge for the Ukrainians will be to bypass or overcome these obstacles at speed, creating momentum that causes Russian command and control to melt down. Satellite imagery shared with CNN shows extensive trenches east of the town of Polohy in Zaporizhzhia region, and thousands of defensive positions over a vast area. These defenses are replicated across a huge stretch of territory, from Crimea in the south all the way to parts of Donetsk. The Russian-appointed head of Crimea, Sergey Aksyonov, has said that “our armed forces have built a modern, deeply-echeloned defense.”