Now, ports generate income according to their size. Except for inter-player trading, this is the only source of income. Lastly, all ships and improvements due this year are completed and put into service. Also, battle damage repairs are made now. Each new step becomes available once certain required advances have been made.
Some classes have unique capabilities or shortcomings.
Port improvements are independent of technology. Any port may have forts and shipyards of any size. Shipyards allow shipbuilding and major repairs, their size determines which number and types of ships may be built. Usually, ships have to reserve movement points for the return trip. The latter type of movement may even double the usual range if a stopover is made at a base.