I started my session in a LFG galleon that was stacking FotD, and it initially was going as usual. But shortly before finishing the first fort, a brigantine showed up. Oddly, it was both shooting and asking for an alliance, but by then the battle was on
Unfortunately, we sank, but the brig just sat there while we sailed back. They hadn't done anything to the fort, but again requested an alliance. We figured out that there had been some miscommunication on their part between the crew, but the alliance nevertheless was formed after yet again trading shots.
5 forts were stacked, though both ships made sure to park with a broadside angle and with constant monitoring of the other side. The tension was eventually defused when fishers from each ship traded bait and helped each other, and we all enjoyed plenty of gold and rep.
Never thought I'd see an alliance between ships who fought not just once, but twice!