Ok, two issues, first about Mongolian empire size. They really never controlled all of China- only the north east. And Empire size isn’t all that important- it’s much more about what one gets out, which, in the case of the mongols, was nil, while in the Roman or British example, there was a huge amount of goods and people available for, well, exploitaion. So, which is more important, land area or population density?
Now, about the military question. It would possibly be a standoff, or more likely an incredibly bloody mongolian defeat. See, the Mongols come streaming out across the steps of Russia, and cut down the 3 legions (60k men) sent to stop them. From there, they head north to sack Poland, which is a mistake since Germany is rallying fast. Then they come charging into Prussia. And die. Hills. Forest. Lakes and rivers. 300 Light, mounted bowmen could not stand up to half their number in expeirenced woodsmen, laying down traps and hiding with crossbows (had those been invented? Oh well…) in the bushes. Of course, that would not happen, because the numbers involved are simply too large for that. Now, as was mentioned, the Mongols move incredibly fast- too fast to bring up seige weapons. Now, strategic surprise is out of the question here- Rome is just too big. Tactical surprise, as in, denying their enemy knowledge of where the attack will come. But Rome has vast resources, and, in its heyday (sp?), was not hindered by coruption, so it could well contend with surpirse by simply reinforcing and fortifying the whole border. Now, what about the pitched battle? One could argue that the mongols have in fact had experience in taking fortified cities, such as those of the Persian empire (hell ,they cracked the great wall- but that was with the help of foreign engineers.) But Persia was taken by surprise…but there’s no real good argument here, except that, well, Persia wasn’t so impressive, right? Right Dan, that’s real convincing. It all boils down to terrain, and time. Persia wins in 6 months, or dies. (Sorry about jumping my ideas around,but I usually don’t fully think posts out before I, well, post) See, the perfect analogy here is Hitler’s Germany to Stalin’s Russia (Mongols= Germany) One’s military is incredibly mobile, but geared only for a fast war, not a long one of attrition and replacement. The mongols have no deep pool of men (or, more importantly, horses) to call upon. I’ll leave it up to others to decide if the mongols could do it, it’s too hot for further thought