The short version is that when I saw Ags Praetorians going after China, I knew that I need Macemen ASAP... I beelined for macemen while my culture continued to eat away at Romes newly conquered cities from China. I think Agamemnons error was waiting to attack until after I had taken out the celts and had a heavily promoted force of macemen and other units that (even though I was fighing the Celts), I was promoting them with the Roman army in mind.

When Agamemnon finally invaded, I was able to destroy most if not all of the invaders with more than acceptable losses of my own forces. This left Rome weak enough that I could bribe his neighbors to the south to declare war on him also, effectively sealing his fate. It's possible that had I invaded, he could have repelled my force, but he wouldn't be able to fight the Aztecs and myself at the same time.