Germany has a submarine problem. During a test dive in October, the Deutsche Marine's U-35 struck something (probably a rock) with one of its four "X-rudders," the steering planes on its rear fins. The damage required the submarine to be towed back to a shipyard in Kiel for repairs—where it joined three other German navy submarines currently drydocked. The U-35 was the Deutsche Marine's only working submarine prior to the collision. The remainder of the German submarine fleet is in port at the German naval base in Eckernförde—waiting for dry docks in Kiel to open up.

Germany has a total of six submarines, all of the Type 212 class. These "hybrid" subs—also operated by the Italian navy—are powered by a combination of a diesel engine and nine proton exchange membrane (PEM) fuel cells. They are among the quietest, most advanced non-nuclear submarines in the world. Because their fuel cells are "air independent propulsion" (AIP), these subs can operate submerged for weeks without surfacing. And since the PEM cell "engines" have no moving parts other than the electrically powered screws, they're incredibly stealthy when submerged. They can also operate in waters as shallow as 17 meters deep (55 feet), making them ideal for patrolling the waters of the Baltic.

But because of backlogs in repairs and a series of unfortunate events, only two of the Type 212 class are not currently under repairs—and they are not ready for active service:

U-31, the class leader—launched in 2002—has just come out of major maintenance and has a year's worth of trials ahead of it before being returned to service. It has been out of service since 2014.

U-32 had a battery casualty on a trip to Norway.

U-33 is in the Kiel shipyard for maintenance until February of 2018 and will likely not be back in service until May or June.

U-34 is due to start a yard period in Kiel in January, and it's not certain when it will return to service.

U-36, the latest submarine built for the Deutsche Marine, was completed a year ago, but it is still in acceptance trials and is not expected to be fully active until May of 2018.

The reason for the backlog: a spare-parts shortage that was exacerbated by cuts made to the Deutsche Marine's budget. To save money, the service stopped stockpiling spares for the complex systems of its subs, relying instead on either purchasing parts on demand or cannibalizing subs that were out of service—much like the US Navy has had to do as a result of budget sequestration over the past four years.

As a result, Germany's entire submarine service is left essentially sitting on its hands through at least the first half of 2018.