Rescue identification patches or "blood chits" as they came to be more commonly known, have been regularly worn by U.S. airmen from WWII right through to the present day.

They were inspired by similar patches and devices carried by pilots in earlier conflicts, but they became ubiquitous during the opening stages of WWII when they were utilized by U.S. pilots of the Republic of China's American Volunteer Group. The American Volunteer Group was a unit of American fighter pilots helping to defend China against Japanese invaders.

A downed aviator in a foreign land, often lost, unable to speak or understand the local language, sincerely hoped that the rescue message on these chits could lead to his eventual rescue and recovery. A blood chit was literally "The Last Hope" of a downed airman and as such, they hold real significance as a souvenir from various wars. They generally displayed a national flag and a rescue message, often in several languages, promising a reward for aiding the downed airman. Originally issued by the Chinese government they were also locally produced.

After the United States entered the war they became an issue item. They eventually spread to all theaters of the war and blood chits continue to be used by American pilots in the modern day.