Downloaded and tried it. I have Downloaded and installed many Offline Missions.
Followed your instructions:
copy or move "war island(us&uk vs jap&germany).mis" file in offmiss
folder. (your offmiss folder is in your AH folder)
and put the 2 remaining files("war island(us&uk vs jap&germany).res"
and war island(us&uk vs jap&germany)(.ver .mis)) in your missres
(which is in your AH folder)
Having followed the instructions, when I try to open the Practice Missions list I just get the White Screen of Death.
When I put the war island(us&uk vs jap&germany).mis in the misstemp, where every one else puts it, same thing.
Have you updated your Mission Editor to the latest version 2.16 Patch 0?