Getting to Ukraine’s deadly “zero line” to fight is so difficult and dangerous that every step requires careful planning and coordination. It often feels like “Mission Impossible,” a Ukrainian sergeant told Business Insider.

When moving toward the zero line, the forwardmost part of the front line where Ukrainian troops are closest to Russian forces, “every single step has to be coordinated. Every like 200 meters, every step, because otherwise it puts you in danger,” the Ukrainian sergeant, call sign Yankee, shared.

That coordination is necessary to prevent unintentional friendly-fire deaths and ensure that maneuvering soldiers have protection…