The Czech Republic, Hungary, Poland, and Slovakia have agreed to form a joint military force.
The deal was announced at a summit in Warsaw on March 6.
It calls for a force of up to 3,000 troops from the four countries to be ready by 2016 for operations such as peacekeeping and crisis management.
The four ex-communist countries – known as the Visegrad Four -- are all members of the European Union and NATO.
The Warsaw summit was joined by German Chancellor Angela Merkel and French President Francois Hollande.
A joint statement said increased multinational defense cooperation is needed because less is being spent on defense during the global financial crisis.
It called for NATO and the EU to cooperate closely to develop defense capabilities without duplicating efforts.
Based on reporting by AFP, AP and dpa