A trove of leaked Pentagon documents reveals how deeply Russia’s security and intelligence services have been penetrated by the United States, demonstrating Washington’s ability to warn Ukraine about planned strikes and providing an assessment of the strength of Moscow’s war machine. The documents paint a portrait of a depleted Russian military that is struggling in its war in Ukraine and of a military apparatus that is deeply compromised. They contain daily real-time warnings to U.S. intelligence agencies on the timing of Moscow’s strikes and even its specific targets. Such intelligence has allowed the United States to pass on to Ukraine...