World War II Order of Battle, Shelby L. Santon, author, Galahad Books, NYNY, publisher, provides the following:
198th Infantry Regiment (Separate).
First Battalion activated in Alaska 9 Feb 43, with personnel and equipment from the 1st. BN, 71st Infantry Regiment; garrisoned Aleutian Islands .
Redesignated as the 206th Infantry Battalion on 26 Jan 44, in Alaska.
Campaigns: Aleutian Islands.
206th Infantry Battalion (Separate).
Activated 26 Jan 44 in Alaska, from 1st BN, 198th IR; departed Alaska 26 Jan 44; arrived Seattle P/E 14 Feb 45 (the 45 may be a typo); assigned to Replacement and School Command, 15 Feb 45 (ditto); inactivated at Camp Shelby, MS, 9 May 45.
PLEASE NOTE: Separate means that the unit was not division based.
That is all I have on your father's military path.