On 7 January, Turkish and Greek coastguard vessels clashed in the Aegean Sea, escalating the tensions between the two NATO members. On 22 December, Turkey announced it would continue to conduct its seismic research activities in the Eastern Mediterranean region, also raising tensions with Greece. The moves came in the wake of an EU announcement on 10 December that it would impose sanctions on Turkey over “illegal and aggressive” actions in the area. This followed clashes between Turkey, Greece and Cyprus over disputed maritime borders in the Aegean and Mediterranean Seas, with the contest over Eastern Mediterranean natural gas exploration only adding fuel to the fire between NATO members. Turkey has thus become a rebellious member of NATO, isolating itself within the alliance as a result of a number of controversial decisions and exacerbating increasing differences among its members. Founded in 1949, NATO was designed to guarantee collective security against the threat then posed by the former Soviet Union to Western Europe and the United States. But the alliance's principles have been challenged by individual actions taken by different member states over recent years. Turkey was against any military intervention in Libya during the 2011 crisis that saw the overthrow of the country's former leader Muammar Gaddafi. However, its priorities changed with the signature of the controversial maritime agreement with Libya's Government of National Accord (GNA) in November 2019. The agreement caused serious tensions with many actors in the resource-rich Eastern Mediterranean region, and it pushed Italy and Greece to establish an exclusive economic zone (EEZ) between the two countries in the Ionian Sea in an accord signed in June 2020. Tensions between Turkey and Greece peaked with Turkey's sending drilling vessels into disputed territorial waters in the Aegean Sea. Greece announced plans to extend its territorial waters from six nautical miles to 12 off its western coastline. France has also voiced its strong condemnation of Turkey's actions in the Eastern Mediterranean, and the United States has condemned Turkey's role in escalating the tensions. These have not only been limited to maritime boundaries, but have also extended to areas of conflict such as in Syria and Libya, where NATO members have had different objectives. French President Emmanuel Macron contested the withdrawal of US troops from northeast Syria in October 2019 that was implemented to avoid clashes with NATO ally Turkey. Consultations did not take place with other allies, including France, which had taken part in the US-led Coalition against the Islamic State (IS) group in the region. Macron said the decision would increase the vulnerability of French troops in the area and would interfere with US logistical supplies to the coalition. French experts criticised the move, saying that the US withdrawal would make Syrian Kurdish forces, a previous US ally in the war against IS, vulnerable to Turkish offensives. NATO disagreements over Syria also opened the door for Russia to increase its foothold in the region, and Russia coordinated with Turkey to launch joint patrols in northeast Syria. The US has also directly criticised other NATO members, saying European members were not paying enough to support it and accusing Germany of being “delinquent” with regard to its contribution. The criticisms were followed by a decision in July 2019 to withdraw 12,000 US troops from Germany, which had failed to meet its defence-spending target. Nearly 5,600 US troops were to be redeployed in other NATO member countries, mostly in Eastern Europe, to address threats to them by Russia. However, the decision has not been implemented because of attempts by US lawmakers to halt the planned troop reductions. The US contribution to NATO is equivalent to 70 per cent of total expenditure, making it the biggest contributor by far. France's contribution represents 5.6 per cent and Germany's 4.8 per cent, pushing the alliance to adopt increases of 4.6 per cent in defence spending by the European members and Canada. The cracks in the alliance have seemed to increase during the Libyan crisis, particularly as a result of Turkey's military agreements with the Libyan GNA and increases in military training and logistical support for it. In March 2020, the EU launched its IRINI naval operation in the Mediterranean to implement the UN Security Council arms embargo on Libya. It has since stopped several ships suspected of transporting weapons to Libya, and tensions rose between Germany and Turkey when a German frigate prevented a Turkish-flagged vessel from entering the area. Disagreements between the NATO allies have also been manifested in the Caucasus, where France has opposed Turkey's intervention in the Nagorno-Karabakh conflict between Armenia and Azerbaijan. Macron said he was concerned at “warlike messages” from Turkey, adding that “we won't accept them.” France is the sole EU representative on the Minsk Group that is helping to mediate between the two sides in order to bring about a peaceful resolution of the conflict. Turkey is an ally of Azerbaijan. Moreover, in 2017, Turkey purchased a Russian mobile surface-to-air missile system, the S-400, for $2.5 billion against the express wishes of the alliance. The US then imposed sanctions on the Turkish weapons-procurement sector as part of the Countering America's Adversaries through Sanctions Act (CAATSA), which sanctions countries undertaking decisions negatively affecting US interests. The tensions that have arisen between members of the alliance have led to some NATO members calling for modifications to the alliance's decision-making process to overcome barriers against action against rebellious allies, thus overriding the principle of collectivity. Meanwhile, most NATO members are putting their hopes on Biden's presidency as part of US President-elect Joe Biden's objective to rebuild alliances lost under outgoing president Donald Trump. While the alliance's unity has been suffering, its role might be reactivated under a newly engaged US presidency. Turkey's actions in the Eastern Mediterranean and its purchase of the Russian S-400 missile system remain the biggest unresolved issues to date, complicating the room for collective action. *A version of this article appears in print in the 14 January, 2021 edition of Al-Ahram Weekly.