If that wikipedia article is accurate (80 million people at a single gathering) no battle comes close. Operation Barbarossa (i.e. the Axis invasion of the Sovie

If that wikipedia article is accurate (80 million people at a single gathering) no battle comes close. Operation Barbarossa (i.e. the Axis invasion of the Soviet Union in WWII) involved as many as 6.7 million troops, but it took place along a 1800 mile front and over the course of nearly six months. It makes sense that you wouldn't get nearly the same density in warfare, especially modern(ish) warfare, as you do in a peaceful gathering.