WWII Bomber gunner adopted special M21 headlight tracers to dissuade German aircraft from attacking the formations.
M21 headlight tracers were developed from standard M1 tracers, except they were filled with 100% igniter compound instead of tracer and igniter compound. They were adopted at the end of 1944. M21 tracers were 3 times brighter than standard M1 tracers. Field reports indicate they caused German bomber interceptors to brake away sooner, leading to less aggressive attacks. Post war surveys and interviews indicate some German pilots welcomed tracers as they shown the formation less defended soft spots and were not as frighted as bomber gunners implied. They were not used after WWII, due to these reasons.