Fleets may carry supply, may carry ground units for invasions (3 factors to carry each ground factor, i.e. a whole fleet to carry an infantry corps - a beach hex containing a port may not be invaded if a 9-factor fleet is in the hex), may give shore bombardment (3 naval factors count as one ground factor in invasions or attacks on coastal fortresses), may sea transport (carry ground units in the combat phase, 2 factors per ground factor - Germany often transports units into Latvia) or may sea escort (a whole 9-factor fleet to help a single ground unit SR over water).