Ukrainian forces prepared for months for a counteroffensive against Russia.
Ukraine on Thursday began its long-awaited counteroffensive against Russia, officials told ABC News.
Well-trained Ukrainian troops had been gathering at strategic locations near the front lines in recent days, Western officials said last week.
Two Ukrainian officials, including a source close to President Volodymry Zelenskyy confirmed to ABC News that an active phase of the Ukrainian counteroffensive is underway.
This is a developing story. Please check back for updates.