Summary: It's the most acute crisis between the West and Russia since the end of the Cold War, and both sides escalated their military deployments Monday. The United States is putting troops on higher alert, NATO says it will reinforce its eastern flank, and Russia is adding to its existing 100,000 troops on Ukraine's borders. Nick Schifrin reports. PBS NewsHour is supported by - https://www.pbs.org/newshour/about/funders
