One reason the defence services have trouble operating jointly is that they don't speak the same language.
If you tell navy personnel to secure a building, they will turn off the lights and lock the doors.
Army personnel will occupy the building so no one could enter.
Special forces will assault the building, capture it and defend it with suppressive fire and close combat.
The air force, on the other hand, will take out a three-year lease with an option to buy.