When displayed with the palm inward toward the signer, it has long been an offensive gesture in some Commonwealth nations. In the 1940s, during the Second World War, a campaign by the Western Allies to use the sign with the back of the hand toward the signer as a "V for Victory" sign proved quite effective. During the Vietnam War, in the 1960s, the "V sign" was widely adopted by the counterculture as a symbol of peace. Shortly thereafter, it also became adopted as a gesture used in photographs, especially in Japan.

On 14 January 1941, Victor de Laveleye, former Belgian Minister of Justice and director of the Belgian French-language broadcasts on the BBC (1940–44), suggested in a broadcast that Belgians use a V for victoire (French: “victory”) and vrijheid (Dutch: "freedom") as a rallying emblem during the Second World War.

By July 1941, the emblematic use of the letter V had spread through occupied Europe. On 19 July, Prime Minister Winston Churchill referred approvingly to the V for Victory campaign in a speech, from which point he started using the V hand sign. Early on he sometimes gestured palm in (sometimes with a cigar between the fingers). Later in the war, he used palm out. After aides explained to the aristocratic Churchill what the palm in gesture meant to other classes, he made sure to use the appropriate sign. Yet the double-entendre of the gesture might have contributed to its popularity, "for a simple twist of hand would have presented the dorsal side in a mocking snub to the common enemy". Other allied leaders used the sign as well.

According to wikipedia