The is not a standard free update; it is identical to the U-Boat Missions Add-On . To upgrade a base game (v1.3 or v1.4) to v1.5, you must purchase this expansion or the Silent Hunter 4: Wolves of the Pacific Gold Edition Official Sources for v1.5
Officially, the 1.5 patch did two things: Silent Hunter 4 1.5 Patch Download
Filename example: SH4_Uboat_Missions_Addon_1.5_International.exe (~700 MB) The is not a standard free update; it
: If you purchase the Silent Hunter 4 Gold Edition on platforms like Steam or Amazon, the v1.5 update is already included . Silent Hunter 4 1.5 Patch Download