The game supports widescreen natively but screen is vert-. You can restore Hor+ by editing one of the ini files. Also the resolution choice in the game menu is limited. The biggest 16:9 resolution is 1920x1080 and for 16:10 is 2560x1600.
To select other resolutions like 2560x1440 or 3840x2160, change it HOVEngine.ini which is in % USERPROFILE% \ Documents \ Hour of Victory \ HOVGame \ Config.
Open the HOVEngine.ini for example in notepad ++ and find these lines to set yor resolution for example.
StartupResolutionX = 2560
StartupResolutionY = 1440
Save it and run the game.
To restore Hor+ go to % USERPROFILE% \ Documents \ Hour of Victory \ HOVGame \ Config, then open HOVInput.ini for example with Notepad++. Now search [Engine.PlayerInput] (It is at the top) and add this line at the very end (of course in [Engine.PlayerInput] section)
Bindings=(Name="F8",Command="FOV 90")
Save it.
When you start the game press F8, this causes that Hor + will be restored.
Of course you can set a different key than F8 and set a higher FOV. The choice is yours.
You will have to press the assigned key (F8 or other) each time you start the game and after loading a new mission, because the FOV will be reset by the game.
To see new FOV effect for aspect ratio 16:9 look at the new screenshoot.