Is it possible start a war patrol in 1945, using SH4 Vanilla?
 

In the vanilla game the dates you can start a war patrol are from 1941 to 1944, is it possible to edit somefiles so that you can start your war patrol in 1945 ?

....not in the Stock game, assuming you are playing SH4 Wolves of the Pacific with Uboat Missions (ver 1.5).

to Start a career in 1945 you would need to play Trigger Maru Overhaul (TMO ver 2.5 by Ducimus) or Fall of the Rising Sun Ultimate (FOTRSU) ver 1.8.

just out of curiosity, why do you want to start in 1945?

Welcome aboard!
 

You need to add an entry in the CareerStart.upc file found in Game \Data \UPCData \UPCCampaignData folder. You could add something like this to the end of the file:

[CareerStart 5]
ID= LateWar
NameDisplayable= 1945
StartTimeInterval=1945-01-12, 1945-01-15
BackgroundPic= 1944.tga
CareerStartBriefingText= The war is nearing the end.
RenownOptions= 1000, 2000, 5000

[CareerStart 5.Flotilla 1]
ID= C5Flotilla1
NameDisplayable= Pearl Harbor
IDLinkFlotilla= PearlHarborCommand
IDLinkUserPlayerUnits= F1Gato, 15, F1Balao, 10
FlotillaBriefingText=
FlotillaCommonality= 1

That should be all you need to do. If you want the other bases, copy the CareerStart 4 data, and change the "4" digits to "5" (there is one of them in each of the header and the ID), and you are good to go. You could add or subtract boats as you wish also, so long as the ones you want to use are "active" in their respective NSS_SubName.upc files. Using the "F1Gato, 15" listing as an example, that refers to "Flotilla 1" (Pearl Harbor), "Gato" boat, and "15" that there are 15 boats available from the Roster cfg file list for the boat. "F2" is Fremantle, "F3" is Brisbane. Brisbane had actually been "downgraded" by 1945 and no longer used as a War Patrol sub base. :salute: