WASHINGTON — A contract solicitation for thousands of Port-a-John bathroom facilities to be placed into Syria could be the clearest indicator yet of U.S. military escalation in the region.

For years, military analysts have pored over documents and imagery to make predictions. Much like imagery showing North Korean missiles being fueled could mean an impending nuclear test, the shipment of Port-a-Johns to a war zone likely signals an influx of conventional US ground troops, experts say.