Turkey operates the second-largest submarine fleet in NATO. Currently all of them are imported designs, but that is set to change. The program to build the first indigenous submarine has been formally launched. Known as MiLDEN (Milli Denizaltı), six of the new boats should join the fleet in the 2030s.

The move comes at a time many defense deals with Turkey are under the spotlight, with the U.S. cancelling sales of F-35 fighter jets to the country and taking away its production role in the program over Turkey’s decision to acquire Russian S-400 air-defense missiles. Turkey also has ambitions to be more self-sufficient in defense, building indigenous frigates and main battle tanks. It even has a railgun project.

The new submarines will have Air Independent Power (AIP), which will allow them to remain submerged for much longer than traditional non-nuclear submarines. Contrary to popular belief, AIP is used to power the electric motor which turns the propeller, not to charge the batteries. The batteries are reserved for silent running and high-speed dashes when the AIP alone is not enough.

Turkey;s 12 current submarines are all based on the German Type-209 family. The plan has been for these to be partly replaced by six of the more advanced Type-214TN model, also from Germany. The Type-214TN submarines will be known as the Reis Class and, unlike previous Turkish submarines, will be built locally. The project has suffered from serious delays however and is not expected to join the fleet until the 2020s.

The MiLDEN program will take years more of research and development. In the meantime the local shipbuilding industry is gaining experience by upgrading three of Pakistan’s submarines. These were built in France so, together with the construction of German-designed boats, Turkey is gaining a broad awareness of submarine design.