FRONTLINE and The Associated Press go inside Russia's war on Ukraine, tracing a pattern of atrocities committed by Russian troops focusing on the Kyiv suburbs, such as Bucha, where some of the most shocking carnage was found.From award-winning director Tom Jennings, producer Annie Wong, AP global investigative reporter Erika Kinetz and her AP colleagues, the joint documentary draws on exclusive original footage, as well as interviews with Ukrainian citizens and prosecutors, top government officials, and international war crimes experts.FRONTLINE and the AP uncover exclusive and harrowing evidence that links possible war crimes in Bucha through the chain of command to one of Russia's top generals — evidence that prosecutors hope might help build a case against Russian President Vladimir Putin in court. But the joint investigation also explores the challenges of holding Putin and other Russian leaders accountable.