Few jobs in history were more dangerous and harrowing than being a submarine crewman for the German Kriegsmarine during World War II. Three out of every four men who signed up for U-boat duty never survived the war, but their effect both psychologically and logistically on Allied shipping and the war effort in general was undeniable. Winston Churchill himself claimed that the only thing that truly frightened him during the entire conflict was, as he put it, "the U-boat peril." Many simulations have been created that let you command a sub in the Battle of the Atlantic, but Silent Hunter III sets a new standard both for this particular type of sim and for the genre as a whole. It hearkens back to the days of Aces of the Pacific, Red Storm Rising, and Red Baron II, where the focus was on simulating what it was like to be a pilot or nuclear sub captain instead of on meticulously re-creating every piece of hardware down to the last rivet at the expense of overall gameplay. That's not to say that Silent Hunter III skimps on the hardware modeling--the attention to detail is fantastic--but it lets you concentrate on the exciting parts of being a sub captain instead of saddling you with loads of tedious duties in the name of "realism."

Too bad that other guy's ship wasn't designed to go underwater.
Up to eight players can play out missions cooperatively in multiplayer mode, which we'll talk about later, but the real meat of the game is in the single-player missions and dynamic campaign. From the very first tutorial mission, which involves navigating the sub into open waters, you know your work is cut out for you. Most of the U-boats in the game are slow, unwieldy, and undergunned compared to the surface ships that hunt them, and it's immediately understood that you sit uncomfortably in the middle of the food chain. At the top are the destroyers, aircraft, and other fast and powerful predators that are out to kill you, and at the bottom are the fat, slow transports laden with troops and cargo that you can send to the bottom of the ocean on a whim.
Only a few single missions are included, based on both historical and hypothetical battles, but a complete mission editor is provided for creating nearly any scenario you like. Those elements would almost be enough in themselves to make for a great game, but the dynamic campaign really lets this game shine. There are some serious quirks, like the fact that loading a save game erases every save game you created after that within the same campaign, but when the gameplay is this good it's possible to forgive faults like these.
The campaign lets you select from various time periods, ranging from the earliest forays in 1939 to the bitter end in 1944. U-boats that are available depend on the time period and the fleet you choose, and there are some huge tradeoffs here. Early on, the Type II U-boats are little more than rickety tubs that carry only a few torpedoes, but their job is eased by Allied forces that aren't quite prepared to deal with the threat. Finding large convoys during the early years is very rare, and many merchant ships travel without escorts and are therefore easy pickings. Destroyers and aircraft early in the war are poorly equipped, relatively untrained, and not all that aggressive, which also helps even the odds.
In the middle years of the war, the subs improve with Type VII and Type IX models, but escort ships abound and they are much better at their jobs. By 1943 your job becomes nearly impossible, as escorts and aircraft have the equipment they need to find you, the weapons they need to kill you, and the will to hunt you down mercilessly.

Successful patrols in the campaign rack up renown points.
Once you've accepted command of a sub, you can modify it based on how much renown you've accumulated in the training missions and also in previous patrols. You gain renown from sinking ships, and then you can spend it on sub upgrades like sonar, engine superchargers, and improved torpedoes. Available upgrades vary from sub to sub, and as newer U-boats become available you can cash in large amounts of renown to trade up. It's a simple system that adds a lot of flavor to the game and really helps you get attached to your sub.
The first sign that this game is truly special comes when you board the sub for your first patrol. You start docked at a home port, and if you climb out of the command room onto the bridge, you can see people lining the docks to see you off. There are women throwing flowers, other sailors chatting it up, and usually even a band belting out the German national anthem as you head out to sea. Ports are modeled like their real-life counterparts, so while it's possible to head straight out from a place like St. Nazaire (site of the famous 1942 British commando raid), navigating into open waters from a place like Lorient requires a lot of tricky maneuvering.

Deck guns are great as long as there are no escort ships around.
Once you hit the Atlantic you are free to plot any course you like to get to your assigned patrol sector, where you generally must remain on station for 24 hours to complete the patrol. The sea is alive with ships that follow dynamically assigned routes, making it possible to track convoys and task forces over long distances to get into optimal attack position. Ships tend to follow historic convoy routes, which are printed on the included paper map, making it easier to position your sub along one of these target-rich (but well-protected) corridors. For a real challenge you can try running through the Strait of Gibraltar, or stalk the coasts of England and Ireland.
Contacts are marked on the map and fade over time if they are not stalked. It also is possible to radio the position of contacts and convoys back to headquarters, and occasionally planes or another sub may be dispatched to deal with it. Unfortunately, wolf packs are not implemented in single-player, making it impossible to team up against a large convoy.
After maneuvering the sub into kill position, one of the game's best elements--plotting firing solutions--comes into play. It is possible to let the computer handle targeting for you, or at least to identify ships, but hardcore players will want to handle everything manually. This is done by identifying targets through the periscope or binoculars using the onscreen ship ID database, which isn't always easy since many attacks are done at night. Once the ship is identified, you send the data to the targeting computer and then measure its range by using the scope to place a line at the top of the ship's mast and another line on the horizon (not easy in choppy seas). Other tools are used to figure out the target's speed and other information, and all of the data you collect is sent to a targeting computer that calculates how much lead the torpedoes must use to hit the target, assuming the victim doesn't change speed or direction while the torpedo is on its way. Getting in close undetected so that torpedo travel time is reduced is vital for success.