Ukrainian troops are probing Russian defenses as spring gives way to a second summer of fighting, and Kyiv's forces are facing an enemy that has made mistakes and suffered setbacks in the 15-month-old war. But analysts say Moscow also has learned from those blunders and improved its weapons and skills.
Russia has built heavily fortified defenses along the 1,000-kilometer (600-mile) front line, honed its electronic weapons to reduce Ukraine's edge in combat drones, and turned heavy bombs from its massive Cold-War-era arsenal into precision-guided gliding munitions capable of striking targets without putting its warplanes at risk.
