The game Cossacks: Back to War was released in 2002 and defaults to a very low resolution (usually 1024x768), which looks tiny or stretched on modern monitors. Because the game engine is old, it does not have a built-in settings menu to change this.
Installing a modern community patch is the most reliable way to eliminate resolution limits and modern hardware crashes. cossacks back to war resolution fix
If you want full-screen stretch (distorted but no bars): The game Cossacks: Back to War was released
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and launch via the shortcut.
"C:\...\Cossacks.exe" -res=1280x1024