Israel agreed Monday to purchase four warships from Germany to protect its offshore natural-gas drilling platforms, in a €430 million ($480 million) deal.

The deal was signed by Israeli Defense Minister Moshe Ya’alon and German Defense Minister Ursula von der Leyen, who is in Israel to mark 50 years of diplomatic relations between the countries.

Defense Ministry Director General Maj. Gen. (Res.) Dan Harel called the nearly $480 million deal “a dramatic leap upward in the navy’s ability to protect the State of Israel’s strategic natural gas sites.”

Under the contract, Germany will provide four advanced Sa’ar-class corvettes to the Israeli navy, to be delivered over the next five years, and will finance approximately one-third of the cost of the deal with a special grant of €115 million.

According to the Hebrew-language news site Ynet, once the vessels are delivered, they will be fitted with Israeli-made weapons systems in a process that will take about a year.

Germany has sold Israel a number of ships and submarines in a series of deals in recent years, most of them partially financed by Berlin as part of Germany’s “special commitment” to Israel in the wake of the Holocaust.

Germany has so far supplied the Israeli navy with five advanced Dolphin-Class submarines, sold at a discount, and was scheduled to deliver a fifth submarine from Germany by late 2014.

In a reciprocal deal, ThyssenKrupp officials promised officials of the Economy Ministry’s Industrial Cooperation Authority that their company would purchase Israeli-made goods, invest in research and development and look into investing approximately NIS 700 million ($180 million) in Israeli companies, Israeli officials said.

President Reuven Rivlin at a welcoming ceremony in Berlin. Rivlin's trip to Germany marks 50 years of bilateral ties. May 10, 2015. Photo by Amos Ben gershom/GPO

President Reuven Rivlin at a welcoming ceremony in Berlin. Rivlin’s trip to Germany marks 50 years of bilateral ties. May 10, 2015. Photo by Amos Ben gershom/GPO

The deal was reported on the same day that Israeli President Reuven Rivlin arrived on a three-day state visit to Germany marking the 50th anniversary of the diplomatic relations between the two countries. He was welcomed there by German President Joachim Gauck.

German Defense Minister Ursula von der Leyen arrived for an official state visit in Israel on Monday as the guest of her counterpart Ya’alon, also to mark the half-century of relations between the two countries.

Minister von der Leyen will visit the Yad Vashem Holocaust Memorial in Jerusalem and meet with wounded army veterans and Holocaust survivors. She will also meet privately with Ya’alon to discuss regional and global strategic and security matters.

Germany’s key role in bolstering Israel’s naval fleet has raised some opposition in Berlin, with senior politicians voicing concern over the possibility that Jerusalem will misuse the German arms.

“Germany must not deliver weapons to conflict areas and to dictators,” Ralf Stegner, of the center-left Social Democratic Party, or SPD, said in an interview in 2014. “What about Saudi Arabia? What about Qatar? I am also asking: What about Israel?”

Stegner clarified that his position is not to be understood to be anti-Israel — “I’m just against arms exports into crisis areas and dictatorship!” he tweeted.

The SPD is part of Chancellor Angela Merkel’s government.

In a 2008 speech in the Knesset, however, Merkel declared that Israel’s security is part of her country’s “raison d’etat” (Staatsraison in German).

Therefore, she vowed, “Israel’s security will never be open to negotiation.”