Boris Gudenuf
Deity
You need to pack 'em in a bit better. According to John Brunner the island of Zanzibar has enough room for Earth's 2010 population of 7 billion people if you stand them upright. I notice that Civ 6 Earth maps never allocate more than one tile to represent Zanzibar the island so.......
I remember Brunner's calculation. Problem is, that's how many people can stand on Zanzibar, it's not how many can fight there. Dupuy and associates in their book The Evolution of Weapons and Warfare calculated the 'dispersion factor' at various points in history (Dupuy's HERO Institute did a lot of work trying to put together a predictive numerical analysis of battles based on historical examples). Basically, they presented it as the amount of space in square kiometers any theoretical force of 100,000 men would take up in 'combat formation'. Here are their figures:
Ancient Armies with swords, spears, pikes, bows:
1.00 square kilometers.
Napoleonic Amies with smoothbore muskets and black powder smooth bore cannon:
20.12 square kilometers
Mid-19th century Armies with black powder rifles, rifled black powder cannon:
25.75 square kilometers
World War One with smokeless powder rifles, machineguns, indirect fire artillery:
247.5 square kilometers
World War Two armies with automatic weapons, tanks, air support, massed artillery:
3100 square kilometers
So basically, the men/tile that can actually fight goes down from Ancient to Modern/Atomic Eras, but more importantly, the number of men any State/Civ can actually get to a battlefield, armed and prepared to fight, goes up even faster. 100,000 men would be a large Corps or small army in WWII (the average US, British or German Army was about 200,000 men) and countries who concentrated on ground forces, like Germany, France, or the USSR, fielded a dozen or more such armies.
By contrast, 100,000 men at any time before railroads could not even be fed more than 20 miles from a coast. seaport, or major river, and in the Ancient Era would represent more troops than most states had men of all ages combined. Athens and Sparta, for two examples, could field about 10,000 Hoplites each, and the average European army on any battlefield in the 18th century was 30 - 60,000 men. Before the mass conscript armies of the Napoleonic Wars, from 500 to 1789 CE only the Battle of Malplaquet in the War of the Spanish Succession had an army with more than 100,000 men on the battlefield anywhere in central or western Europe.