The United States joined its European NATO allies in conducting a large-scale defense drill on the border between Poland and Lithuania, simulating the possibility of a Russian invasion in the region, which if successful, would sever Estonia, Latvia, and Lithuania’s access to other allied nations.

U.S. and British troops were joined by troops from Poland, Lithuania and Croatia in the training effort, which involved defending a band of land called the Suwalki Gap that runs for about 65 miles through farmland, woods and low hills.  That narrow stretch of territory could serve as a flash point in any potential future conflict with Russia in the area, as capturing it would cut off supply lines to the Baltic States from their Western partners.

“The gap is vulnerable because of the geography. It’s not inevitable that there’s going to be an attack, of course, but … if that was closed, then you have three allies that are north that are potentially isolated from the rest of the alliance,” U.S. Lieutenant General Ben Hodges told Reuters.

U.S. Army Europe commander Ben Hodges speaks to U.S. soldiers on June 16th

“We have to practice, we have to demonstrate that we can support allies in keeping (the Gap) open, in maintaining that connection,” he said.