Recently, Turkey has been the troubled child of NATO. The aftermath of the alleged coup from July 2016—which saw a crackdown on thousands of government officials and journalists imprisoned—had caused distress among the allies. Then, in November 2017, Ankara announced the completion of a deal with Russia that would see the purchase of four S-400 surface-to-air missile batteries by the Turkish government for US$2.5 billion. Announcing a done-deal without prior informing let alone receiving a green light by NATO is an affront to the alliance—not only because relations with non-NATO member Russia are at all-time low, but more importantly because the S-400s are not compatible with any NATO-owned systems.

Add some bilateral rows with Germany on imprisoning several German citizens without charges, and with the US on consular tit-for-tats. And now, another situation Turkey has added to the list could lead to NATO members ending up on opposing sides in a conflict for the first time. In mid-January, the Erdogan government launched Operation Olive Branch, which has now entered into its third week of fighting. The Turkish military has launched attacks on what it classifies as terrorists: targeting the Syrian Kurdish Democratic Union Party (PYD) with its armed People’s Protection Units (YPG)—which President Erdogan claims belongs to the Kurdish Workers’ Party PKK—and ISIS posts on Syrian territory. Ankara argues that the military campaign is necessary to protect Turkey’s national security interests and would “serve to secure NATO’s southern border,” while many fear it is rather a continuation of Turkey’s decade-long feud against, and suppression of, the Kurds. Furthermore, Turkey referring to the right of self-defense because of the “threat of terrorism” doesn’t comply with Article 51 of the UN Charter, and makes the operation a “blatant violation of a fundamental principle of international law.”

Despite that, almost all of Turkey’s allies have remained cringingly silent on the aggressive campaign, especially Washington that until recently trained and armed the now targeted Kurdish militias, with the YPG having been a major partner in the U.S. led fight against ISIS. French Foreign Minister Jean-Yves Le Drian called for the need to discuss the matter at the U.N. Security Council. While politicians in Berlin are still trying to form a government after September’s elections, the “managing” government in Berlin faces two dilemmas. One of its allies is driving an aggressive campaign which has already seen civilians among the victims, most recently in Afrin, and secondly, the fact that German-exported Leopard-2 tanks are being in used in the campaign, as confirmed recently by the Turkish government.

The fluidity of present conflicts could quickly become an issue for any arms exporter in the world. The same weapons, or allied arms, being used on both sides of the conflict, or long-time allies suddenly facing each other on the battlefield. (Australia with its recent announcement on expanding their defense industrial base and increasing arms exports should particularly take note.)

Germany has been exporting Leopard tanks to Turkey since the 1980s, explicitly including a clause in the contracts that the tanks may only be used for defense purposes. However, different rules apply to the Leopard-2, exported from 2006-2011, which are exempt from that clause, instead prohibited from being sold or gifted to third parties, an uncomfortable situation for Berlin. The Leopard-2 tanks were now due for an upgrade, which alongside German arms sales in general to Turkey have been halted for now. Further actions are only expected after a coalition treaty between Social Democrats and Angela Merkel’s CDU has been signed.

In an unprecedented decision in 2014, the German parliament had agreed to arm Iraqi Kurdish Peshmerga, not to be confused with the aforementioned Kurdish militias. Then, Berlin cited the brutality of ISIS against civilians and the impending collapse of Iraq as an argument on why they would break with the tradition of not exporting arms into conflict zones.

While the YPG  currently has no access to German arms, they indeed have weapons to face the Turkish army: Unlike Berlin, Washington did indeed equip the group with arms and vehicles. Consequently, the Turks are faced with arms by an ally. Berlin, however, could be in similar circumstances very quickly. Turkish President Erdogan vows to expand Olive Branch beyond the enclave of Afrin, potentially all the way to Iraq. An extension of the operation could then also potentially see German arms facing each other. If Erdogan were to drive Olive Branch to the Iraqi border, without a doubt, the Peshmerga would not sit idle and watch. Officially, they are only allowed to use the German arms in actions against ISIS and to protect civilians, with the validity of this clause challenged with a potential attack by Turkish forces.

And what’s worse, going beyond Afrin could have Turkish troops facing their NATO allies on the frontline. Hundreds of U.S. soldiers are in Manbij, just 130km east of Afrin, where they have been supporting the YPG in their fight against ISIS. It would be a historic first, with the potential for a true NATO crisis.