If you're really interested in drawing a parallel between reality and Civ, take a look at the world. Are there any civilizations that rely on spearmen today? No? Good. With that in mind, let's assume there's probably never going to be a real world empirical test of spearmen versus GDRs. In real reality-you simply can't have a technological gap where a civilization that takes up about 5% of the world are completely baffled by the idea of muskets while the rest of the world is using stealth bombers. You can say they're using older technology and not nearly as well organized militarily-but they're not still using spears. In fact, if you want a real world analogy-look at today's news. The US, (and the USSR before them) should have steamrolled through Afghanistan in 2 turns without taking so much as scratch of damage, right?