Ankara / Moscow / Washington (AP) - An explosive conflict between Turkey and the US is at its peak: The first delivery of the Russian missile defense system S-400 arrived on Friday in Ankara.

This threatens Turkey's US sanctions, which could put a further blow to the already fragile economy of the country. Some even consider erosion of the alliance possible because of the dispute between the two NATO partners. They note bitterly that Russia has managed to drive a wedge into NATO.

The US government is strictly against the use of the S-400 in Turkey. Among other things, she fears that Russia could spy on the new American F-35 jet via the system's sensitive radars. Turkey is a partner in construction in the US and should get around 100 pieces. On the other hand, it is also about supremacy in the arms market. Under NATO countries, the US had a monopoly there so far.

Why is Turkey so keen on the deal?

Turkey stresses that it needs its own missile defense - against threats from the neighboring civil war country Syria, but also from within. Since the coup attempt of 2016 she is extremely focused on security. Negotiations with the US over the purchase of their Patriot missile defense system went nowhere. Italian and Spanish patriots continue to be stationed in Turkey as part of the joint NATO air defense - but the government argues that they only protect 30% of the airspace.

A NATO employee who does not want to be named by name says he also sees "a geopolitical strategy." One aspect is that Turkey wants to create a broader common ground through the billion dollar deal with Russia. Among other things, it is about cooperation in northern Syria, where Russia and Turkey support different parties near the Turkish border. In addition, it is about natural gas from Russia and the high energy needs of Turkey. And of course Turkey would see "that the US is losing importance in the region and wants to withdraw from Syria to Afghanistan".

And Russia?

Above all, Russia wants to expand its position as a weapons and armaments exporter. To win over a customer like Turkey from the ranks of NATO is a breakthrough for the manufacturer, the state-owned Russian arms company Almas-Antej.

Which sanctions exactly do the US want to impose?

There are different punishments in the conversation. First, the Pentagon wants to throw Turkey out of the F-35 program. It should be ready by the end of July. First steps are done.

In addition, the S-400 deal could trigger sanctions under the CAATSA (Countering America's Adversaries through Sanctions) Act, which targets deals with the Russian defense sector. These sanctions include, for example, bans on real estate transactions, export license restrictions and visa restrictions.

According to the law, US President Donald Trump would have the option of putting penalties on ice by decree. Whether he will do that is unclear. After a conversation with Erdogan on the sidelines of the G20 summit in late June in Japan, Trump Erdogan's decision to buy the S-400 was defended after all: his predecessors had denied Turkey the Patriot system. Erdogan had been treated unfairly.

The US State Department is still on penalties. There has been repeated talk of "very real and negative" consequences. Pentagon spokesman Mike Andrews told the German Press Agency: "Turkey will not be allowed to have both systems."

But you do not hear much from NATO so far - why?

In principle, every NATO country can decide for itself which equipment it buys. At the same time, the conflict in NATO is seen as a bilateral issue. The dispute should not be brought into the Alliance. "All sides are very interested in the fact that the alliance is not damaged," says a NATO diplomat. Nevertheless, Secretary General Jens Stoltenberg has repeatedly expressed concern. During a visit to Turkey in May, he said that it had to be avoided that one NATO partner imposed sanctions on another. After the delivery of the S-400, the solution could only look like Turkey does not install it.

And what does Germany say?

The German government has made several criticisms and hopes to the very end that Turkey rethinks its decision. "It is very important for NATO that their armed forces have interoperability," government spokesman Steffen Seibert said at the end of May in Berlin. But concrete sanctions have not been announced by Germany.

What is the S-400 exactly?

The S-400 is a mobile air defense system that can shoot planes, missiles and other objects from the sky. The Russian armed forces had put it into operation in 2007. It ignites short-, medium- and long-range missiles that can destroy targets at a greater distance and altitude than the American Patriot system, according to Russian sources and also in international trade magazines such as Defense IQ. In addition, the system costs considerably less.

The delivery quantity is different. The general director of the state-owned Russian technology group Rostech, Sergei Chemezov, told the business paper Kommersant that Turkey will receive four units for a price of 2.5 billion US dollars. One unit has the agency according to Interfax twelve launch facilities with four missiles. The Cumhuriyet reported recently that Turkey has ordered "two S-400 batteries" with a capacity of 72 missile launches each.

Are the concerns of the US justified? Would the F-35 bomber be endangered - and thus part of NATO's security?

Yes, say the US. No, says Turkey. Military technology expert Sebastien Roblin writes for "The National Interest" 2018: If Turkey jointly operates the S-400 missile defense and the F-35 fighter jets, the S-400 could regularly collect data on the jets in the air on the ground - Example of when the stealth jet will be visible on the radar. Turkey may not want to share the data with Russia at all. "However, it seems possible that the highly networked computers of the guns have backdoors that give access to the Russian military." It is also agreed with Moscow that Russian experts will take care of the maintenance of the S-400.

Turkey is trying to dispel concerns: Foreign Minister Mevlüt Cavusoglu said last week that the S-400 would only be activated in an emergency. In addition, they should not be integrated into the networked air defense with the other NATO partners.

Daily Sabah with Turkish view on S-400

Cumhuriyet to the S-400 Air Force Base in Ankara

Eliot Angel statement on Trump Erdogan meeting

Lawfare blog on Turkish-American tensions and F-35 measures

The National Interest on Risks of Joint Operation of S-400 and F-35

German Marshall Fund analysis on the roots and future of the S-400 crisis

Defense IQ magazine with technical details about S-400