https://www.gamespot.com/articles/why-its-called-battlefield-v/1100-6459247/

The Battlefield franchise does not normally use Roman numerals for its titling convention, but that's changing this year with the World War II game Battlefield V. But why? The official Battlefield Twitter account has the answer--and it fits with the game's WWII theme.

The "V" is connected to the V sign, which stands for "V for Victory." UK Prime Minister Winston Churchill, who led Britain during WWII, helped popularised this for the Allied forces.