Military co-operation between the Axis powers of WW2

[Rodion Romanovich]

There was cooperation on most fronts:
- Fall Gelb - after the allied front had broken the Italians attempted a supporting offensive through the alps, but failed to achieve any break-through
- Eastern front - there were Italian and Romanian troops covering one of the critical areas at the flank of the Stalingrad pocket during Soviet operation Uranus, but it probably wasn't their fault though that they couldn't hold the massive USSR offensive. There were Romanian and Italian troops in other parts of the eastern front too.
- The German invasion of Greece that postponed Operation Barbarossa was due to the Italians failing there.
- The most successful cooperation between the axis was perhaps Rommels Afrika Korps consisting of both Germans and Italians. Again, Rommel moved in because the Italians failed. There was some successful cooperation between the Italian fleet and Luftwaffe in the Mediterranean.

...those are all examples I could think of right now...