Germany has come up with a new approach to joint defense operations and East European fears of the renewed Russian threat. The Germans have quietly agreed to experiment with integrating combat brigades from smaller EU (European Union) members. Initially this means a Romanian mechanized infantry brigade will become part of the German Rapid Response Forces Division and a Czech Rapid Deployment Brigade will join the German 10th Armored Division. This gives East European allies (all NATO and EU members) the extra assurances that mutual defense pledgees will be honored and, unofficially, enable East European troops to observe up close and on a daily basis, how willing and able the German armed forces are to move east to defend a European ally (rather than invade Russia, which is all the Russians can remember). This sort of thing is nothing new and efforts at such integration have been going on, and increasing, since the end of World War II in 1945. This integration approach is, however, more ambitious than earlier efforts.
After NATO was created in 1948 European nations expected their armed forces to regularly operate closely with those from other European nations. That effort expanded after the Cold War ended in 1991 and NATO members sharply reduced their armed forces and cut defense spending. It was an economic matter at that point.
In 1993 the European Union was created and it found itself in the midst of a crises next door in the former communist state of Yugoslavia, where a civil war had broken out. The EU was meant to be an economic/political union but despite the existence of NATO, the EU has purely European and had more European nations as members than NATO did. Plans were soon underway to establish some EU military cooperation alliances as well.
By 2000, fresh from the peacekeeping crises in the Balkans, the EU succeeded in gathering a considerable number of assets for its new Rapid Reaction Force but found that post-Cold War European nations lacked much in the way of support forces. That was because most of what they had was already pledged to NATO. So the new EU force was mainly from larger nations. The contributors included Britain (an armored brigade, a marine brigade, 72 warplanes, an aircraft carrier, two SSNs, four surface warships and five support and amphibious ships), France (12,000 troops including tank and engineer brigades, 75 warplanes, 12 warships including an aircraft carrier), Germany (13,500 troops), Italy (6,000), Spain (6,000), Netherlands (5,000) and smaller contributions (totaling 12,000) from Greece, Austria, Finland, Sweden, Belgium, Ireland, Portugal and Luxembourg. Denmark was the only EU member to refuse to contribute but Turkey, seeking to join the EU and long a member of NATO offered a mechanized brigade and 30 warplanes.
This EU force quickly evolved into EU Battlegroups, a system where by the Rapid Reaction Force members arranged to take turns contributing two or three “battlegroups)” (a reinforced combat battalion) to be available for six months for quick deployment. This went into effect in 2005 and is still operational. After 2014 the focus turned towards potential emergencies involving the new Russian threat. That encouraged Germany to offer an integration option, which several East European nations expressed an interest in.