https://en.wikipedia.org/wiki/Franco-German_Brigade: operational since 1989, German troops stationed on French soil since 2009.
https://en.wikipedia.org/wiki/I._German/Dutch_Corps: 30,000 troops (mostly German, I would guess, but several time with a Dutch commander)
https://en.wikipedia.org/wiki/BeNeSam: Belgian and Dutch navy cooperation since 1948, with a joint commanding officer since 1996 (https://en.wikipedia.org/wiki/Admiral_Benelux). Chances are this, eventually, will lead to a merger of armies, navies, and air forces of Belgium, the Netherlands, and Luxembourg.
https://en.wikipedia.org/wiki/Franco-German_Brigade: operational since 1989, German troops stationed on French soil since 2009.
https://en.wikipedia.org/wiki/I._German/Dutch_Corps: 30,000 troops (mostly German, I would guess, but several time with a Dutch commander)
https://en.wikipedia.org/wiki/BeNeSam: Belgian and Dutch navy cooperation since 1948, with a joint commanding officer since 1996 (https://en.wikipedia.org/wiki/Admiral_Benelux). Chances are this, eventually, will lead to a merger of armies, navies, and air forces of Belgium, the Netherlands, and Luxembourg.