Night vision technology has evolved from early searchlights and flares used in World War II to modern thermal imaging systems. Early night vision devices had many disadvantages as they required additional light sources that revealed tactical positions. Later generations used image intensification and then thermal imaging to provide clearer night vision without added light. Current US military forces use Generation 3 night vision, which offers longer usage life than Generation 4, despite some image and noise tradeoffs. Night vision has expanded from military to civilian uses including law enforcement, hunting, and search and rescue.