A total of 250 Czech army paratroopers on Monday left for Slovakia, which neighbors war-ravaged Ukraine, to build a NATO battle group there, the defense ministry said.

The battlegroup will comprise up to 2,100 soldiers from Germany, the Netherlands, Poland, Slovakia, Slovenia, and the United States.

The Czechs will be in command of the battlegroup.

“The key task of the mission is to declare the readiness, resolve, and unity of NATO members in protecting the territorial integrity of the alliance,” said Colonel Tomas Unzeitig who will lead the battlegroup.

“This is an international NATO operation set to boost the defense capacities of the Slovak Army,” he added.

The mission is part of NATO’s bid to boost its eastern flank following the Russian invasion of Ukraine, which started on February 24.

The ministry said the paratroopers will stay in Slovakia until June and then will be replaced by a unit operating armored vehicles.

The Czech Republic joined NATO in 1999 and Slovakia followed suit in 2004. The two countries that formed Czechoslovakia until a peaceful split in 1993 are both EU members.