Submarines

An important area of warfare i missed out was submarines, its not seperate from naval warfare but it does have a different area and is a gamechanger in both naval warfare and empire building. To understand submarines role the two main goals of naval warfare must be known; the first is the allowance of your shipping to pass across the seas, theses can be transports, merchants or even troops and supplies, the second goal is the denial of the use of the seas to enemy shipping. Before submarines the acheivment of sea dominance meant both of these goals was accomplished, this was the basis behind the British empires massive navy (had to be able to fight the next two biggest fleets at the same time). Submarines changed this, think both world wars and the wolfpacks, because while you could acheive sea dominance and deny the enemy use of the seas the enemy could still threaten and deny effective use of the seas to shipping, while they can't easily destroy warships it dosen't matter if your supplies can't get through. while there are effective countermeasures to submarines they require certain tactics, such as escorts or convoys, to be effective and are greatly enhanced by knowing where the subs are or are going to. This makes them a great defensive weapon, especially for a weaker power, and if submarine colliers or enhanced ranges are built in they become potent offensive weapons. Australia could do worse than get a defensive (low range in exchange for cheapness, for numbers, and weapons) sub fleet to ward off other powers. Submarines are mainly diesel or nuclear powered now, so biodiesel will be neccesary for current designs to be used which certainly acheivable to some extent and if the fuel usage is reduced across the whole fleet (say by using wind) would be easier, or alternate power sources. But an important lesson is the first military submarine, it was hand powered by a single man and was supposed to attach explosive charges to british warships during the war of independence. It completly failed to destroy any warships but it was a good first try. As we can see low tech submarines are possible but warships themselves are hard to kill (the new russian torpedoes may change that) and the best historic success has been in the denial of safe shipping to the enemy.