Took me a few tries, but I beat it, playing against Aegisbot. I didn't retreat the army, just built as fast as I could. I defended the river crossing with manned towers and 2 manned ships, fortress, massed troops. I used a phalanx of Spartan Hoplites set to defensive blocking the beach, backed with heavy skirmishers, swordsmen, cavalry, several healers. Built a 2nd civ center to the north early on. Built a bunch of rams and charged, then sent another wave, then a third which totally broke their resistance, mopped them up. Ships might seem wasteful, but really weakened them - killed woodcutters who came near, started whittling down their attack forces before they even reached the crossing. Troops on the ships took no losses, and I could repair the ships between attack waves.