Since Feb. 24 NATO has readied 140,000 troops in the region and mobilized a war chest of advanced military equipment in preparation. The U.S. service members and NATO troops are currently deployed in neighboring member countries. The alliance has more than 140 warships and 130 aircraft.

Ukraine is bordered by four NATO allies; Poland, Slovakia, Hungary and Romania. Poland currently hosts the majority of the troops from the 30-nation alliance.