I really hate to say it. This is the one area of Civ V that needed the most work, and it is no better than it was in Civ V. For the third or fourth time, an enemy Civ has declared war on me and gotten 5-10 units near one of my cities. With just a basic strategy of rushing the city, they could have easily taken it. Instead, they get within range, and incredibly, just move around. Maybe one or two will actually attack the city. The rest wander around, move back and forth, and get killed by my archers. I can defend any city in the ancient era with two archers, even vs. 10 enemy units. Very disappointing.