TOKYO -- When U.S. President Joe Biden faced reporters Thursday at NATO headquarters in Brussels, the first question he received was on chemical weapons.
Ukraine war
Why chemical weapons constitute a red line: 5 things to know
Russia thought to have sarin, VX, mustard gas and others in arsenal
If conventional methods stall in Ukraine, Russian President Vladimir Putin has two options, analysts say: humiliating retreat or escalation to weapons of mass destruction. (Source photos by Reuters and AP)
Read Next
Latest on Ukraine war
