Israel has a policy of not commenting officially on its nuclear weapons program. Documents from the archives of the German Foreign Ministry make it clear, however, that the German government has known about the program since 1961. The last discussion for which there is evidence took place in 1977, when then-Chancellor Helmut Schmidt spoke to then-Israeli Foreign Minister Moshe Dayan about the issue.

The submarines are built by the German shipyard HDW in Kiel. Three submarines have already been delivered to Israel, and three more will be delivered by 2017. In addition, Israel is considering ordering its seventh, eighth and ninth submarines from Germany.

The German government recently signed the contract for the delivery of the sixth vessel. According to information obtained by SPIEGEL, Chancellor Angela Merkel made substantial concessions to the Israelis. Not only is Berlin financing one-third of the cost of the submarine, around €135 million ($168 million), but it is also allowing Israel to defer its payment until 2015.

Merkel had tied the delivery of the sixth submarine to a number of conditions, including a demand that Israel stop its expansionist settlement policy and allow the completion of a sewage treatment plant in the Gaza Strip, which is partially financed with German money. So far, Israeli Prime Minister Benjamin Netanyahu has met none of the terms.