The surge in activity in Saudi Arabia’s military policy is only one of the elements that could trigger significant geopolitical upheaval in the Middle East, Southeast Europe, and large expanses of the post-Soviet world. The second element is Turkey’s foreign-policy efforts.
Both countries demonstrate very impressive growth in military spending. Ankara is increasingly active in the Balkans, the Black Sea, the Caucasus, and Central Asia. Ankara’s current policy is notable for its distinctly two-pronged approach: on one hand there is a desire to remain a US ally, but on the other - we see attempts to garner political capital through criticism of the United States and an unmistakable rapprochement with Washington’s opponents. This is reinforced by the Turkish elite’s deep-rooted perception that Turkey deserves a «central place in Eurasia as a whole, as well as in Europe and the Balkans, the Black Sea and the Caucasus, the Eastern Mediterranean, the Middle East, and in Central Asia in particular», claims the well-known diplomat and head of the Turkish International Cooperation Agency, Umut Arik. 
Thus, Sam Perlo-Freeman, the head of the SIPRI Military Expenditure Project, is in no way blowing events out of proportion when he warns of the threat of «regional arms races».
Ankara is keeping a close eye on every step Saudi Arabia takes. Özcan Tikit, a columnist for the Turkish newspaper Habertürk, notes that «the Saudi leaders’ demands have raised concerns for Obama», because the Saudis have already spoken out against US policy in the Middle East.
Özcan Tikit characterizes Saudi Arabia’s foreign-policy priorities as follows, «Riyadh has entered the fray, but has set two red lines. One of those is defined as the imperative to battle against the antimonarchical movements and their ideology, such as, for example, radical organizations like al-Qaeda and the Islamic State, the Arab Spring movements, and the Muslim Brotherhood. Hence her distrust of popular movements that have arisen in the Islamic world. Riyadh is focused on eliminating such threats, regardless of their Islamic country of origin, and is truly diving headlong into any international alliance. The presence of the other red line stems from the existence of Iran ... In 2005, the Saudi king, now deceased, called Iran «Saudi Arabia’s main enemy» and «a snake whose head must be cut off». There are many reasons why Iran was declared an enemy, but the most important was due to Tehran’s imperial policy that focuses on Shia Islam. Riyadh fears that the Iranians are inciting an uprising among Saudi Arabia’s Shiite population. And a powerful Iran spells disaster for the Saudis. Riyadh also sees Assad’s regime in Syria as a threat, believing him to be an Iranian lackey. The Saudi leaders dream of a Syria in which an emirate could be created, or perhaps under the rule of a dictatorship, as in Egypt. 
At the same time, events in Yemen, where pro-Iranian forces have achieved significant military victories, as well as the growing internal contradictions within Saudi Arabia herself, could entail serious adjustments to Riyadh’s strategy, which in turn will change the balance of power in the Russia - US - Turkey - Saudi Arabia quadrangle. There is reason to believe that in the future the Turkish aspect of its foreign policy will be more meaningful for Washington than the Saudi element. Zbigniew Brzezinski was partial to that view in the late 1990s, noting that Ankara «stabilizes the Black Sea region, controls access from it to the Mediterranean Sea, balances Russia in the Caucasus, still offers an antidote to Muslim fundamentalism, and serves as the southern anchor for NATO». 
Since then, Turkey’s significance for US foreign policy has further increased, which is also in part due to Washington’s missteps in the Middle East. German expert Volker Perthes writes, «The United States is no longer merely a hegemonic power. It has become a regional power and a de facto neighbor of Iran, Saudi Arabia, and Syria». The US must also take into account the fact that, according to experts from the US National Intelligence Council, by 2025 the «Greater Middle East» could become the stage for a full-blown nuclear arms race involving both Turkey and Saudi Arabia, which by that time will have unleashed their «own nuclear weapons program».
In this context, Turkey’s growing engagement in European affairs should also be noted (ranging from her traditional interest in the Balkans to her role in energy projects). Here the interests of Ankara and Riyadh are more at odds than complementary. In particular, the Eurasian Islamic Council, created at Turkey’s initiative in 1995 and which brings together the Muslim communities of the Balkans, the Caucasus, and Central Asia, was intended to counter the Islamic Council for Eastern Europe, created under the wing of the Muslim World League («Rabita»), which is supported by Saudi Arabia.
The battle for the European market is an important area of rivalry between Ankara and Riyadh. According to data from 2013, in terms of total commerce, Turkey ranked sixth on the list of the EU’s trading partners, at 128.156 billion euros. The EU does only half as much business with Saudi Arabia (63.833 billion euros), but this figure is high enough to put the Saudis in 11th place, ahead of, specifically, Canada, Algeria, the UAE, Australia, and South Africa. There can be no doubt that in the coming years both Turkey and Saudi Arabia will further their trade and economic expansion in Europe.
Both Ankara and Riyadh can also be expected to become more interested in playing upon the tensions between the US and Europe. The Paris-based newspaper Libération has written about how Europeans view these tensions, «Europeans are placing their bets on African stability, because they are literally sitting on the other shore in their relationship to that continent, while the Americans are washing their hands of the region. Americans are trying to play the Iran card, believing her to be more capable of ensuring stability in the Middle East than Saudi Arabia. The Europeans, for their part, are supporting the Sunnis because they do not want a region so close to them to have only one ‘master’ - Iran. The Americans are taking a much tougher stance on Russia than the Europeans because they have far fewer economic ties there. They do not want Russia’s competition on the international stage, and they care much more about the stability of Asia than the wellbeing of Europe». The primary conclusion drawn by Libération on this matter reads as follows, «The regional chaos generated by new border squabbles will give rise to global chaos» that will lead to a weakening of the transatlantic relationship. 
 Arik U. Turkey and the International Security System in the 21st Century // Eurasian Studies.1995/96.№ 4.P.8.