Wherever possible, a supply route will be created over land instead of a sea route. This is true even when the land route may be much longer than a sea route (e.g. when wrapping around the Mediterranean Sea, for example). In Semper Fi, it is possible to avoid this problem and manually route supplies via the sea.
'''Ports:''' Overseas supply functions with an origin port and a receiving port.
The most efficient origin port is a national core province with IC, thus acting as a supply depot, with high infrastructure and port level. While an origin port can theoretically send an unlimited number of convoys, a receiving port overseas can only receive one supply convoy and send out one resource convoy. Manually trying to game the system and make two supply convoys by ticking the appropriate boxes does not work. The supplies an overseas port can receive is limited by port level, with 4 supplies per day per port level. A level 10 port can thus receive no more than 40 supplies per day which can, for example, support about 15 infantry divisions with artillery. Therefore, large overseas forces require more ports in areas linked to your port ( = more possible supply convoys) or supply them by air.
'''Supply Convoys:''' Supply convoys use a number of transports equal to the length of the route (measured in terms of sea provinces) in order to operate at maximum capacity for the receiving port (determined by port level, as described above). Starting in Semper Fi, if units overseas need more supplies than the local supply depot can provide, additional supply convoys can be sent to other overseas ports. ''This will not create new supply depots overseas,'' but these will overcome the bottleneck introduced by the port size of the supply depot. Thus, all additional ports opened will funnel supplies to the local supply depot, which will then disperse supplies as needed.