Tour of Duty
This can be done in custom(solo) matches on any game type, all you have to do is load up all 6 Halo 2 Anniversary maps, and end the game.
The required maps to obtain this achievement are:
LOCKOUT ANNIVERSARY (Under Lockdown)
ASCENSION ANNIVERSARY (Under Zenith)
ZANZIBAR ANNIVERSARY (Under Stonetown)
COAGULATION ANNIVERSARY (Under Bloodline)
WARLOCK ANNIVERSARY (Under Warlord)
SANCTUARY ANNIVERSARY (Under Shrine)
Remember these listed are all in Custom Games>Halo 2> Anniversary
Any questions or concerns? Comment or send me a message.