An interesting observation from my Year of the 4 Emperors game. As Vitellius I have several cities along the Rhine, some with ports onto the river. But when they are besieged, the city's supply goes to zero. This seems to be different to coastal cities with ports where the seaport provides some supply and a naval blockade of the port is required to reduce total city supply to zero.
Is there really a difference between seaports and river ports or am I missing something?
See the screenshot below. Vagiones has a port as the tooltip says. There are no barbarian river boats blocking the port but supply is zero.
https://photos.app.goo.gl/APBvd8exClakYZlo1
Other than that the game is going well. I'm particularly pleased with my last couple of moves which have involved landing legions from Britain to deal with the uppity north German barbarians...