Two games in a row now, using vanilla 1.15 in the July start scenario, playing USA against CSA AI, the CSA have launched an all-out assault on Fortress Monroe. In the game I'm currently playing, it is July 1862, and Lee and Beauregard with 70,000 rebs have been down on the James peninsula trying to get into Monroe for two months while McClellan with the Army of the Potomac have slowly worked their way down from Manassas to the space adjacent to Richmond.
Last time I played it was the same thing, except that with a smaller garrison I ultimately lost the fort - though the rebs lost something like 10,000 men. I can't imagine the "game is worth the candle" in either case.