Russia's intervention in Syria, which began in the final days of September, may have overturned the chessboard in one of the most delicate but till now skillfully managed economic and political relationships in Europe. Though Russia seems to have been planning its move for at least six months, the change came without warning. When President Recep Tayyip Erdogan paid a one-day visit to President Putin in Moscow on 23 September, the two countries seemed to have a good working relationship, based mainly on energy cooperation and trade. Russia was Turkey's sixth largest trading partner in 2013, and last year bilateral trade between the two countries reached $31 billon. This year's performance looks likely to be poorer, which was one of the motivations for Erdogan's visit. GAS DEPENDENCE: MORE IMPORTANT THAN THE STAtistics for the volume of Turkish-Russian trade is Turkey's dependence on energy imports from Russia. More than half of Turkey's natural gas is imported from Russia (some estimates put it as high as 60 per cent). The gas reaches the country through several pipelines, the most important being Blue Stream that travels under the Black Sea and was due to be expanded. Turkey also hoped that a new Turkish Stream network would be agreed, though negotiations over it appeared to have stalled over the summer. Turkey also signed an agreement in 2010 for Rosatom of Russia to construct a 4,800-MW nuclear power plant on the Mediterranean. Russia, which is putting up 93 per cent of the finance for its construction, has so far spent around $3 billion on it. Projects of this kind and the expansion of bilateral trade, rather than the situation in Syria, still dominated the agenda while President Erdogan was in Moscow. Though the two sides, as always, agreed to differ over Syria, the atmosphere was warm enough for Erdogan to suggest that Syria's President Bashar Al-Assad might be allowed to stay on for a “transitional period” in the event of a Syrian settlement. This was a major departure from Turkey's unwavering stand against Al-Assad. But on his return to Ankara, Erdogan returned to his insistence that Al-Assad must go. RUSSIA'S SURPRISE MOVE: Less than a week later, Russia's intervention in Syria completely changed the picture. It would hardly be surprising if the Turkish president felt very angry about the way he was misled in Moscow about Russian intentions. Ten days after his Moscow visit, President Erdogan was accusing Russia of making a “grave mistake.” Two days later he went as far as to say that Russia might “lose Turkey's friendship.” The Russian presence in Syria upsets Turkish foreign policy at several levels. First, Russia and Turkey are historical enemies who in the 20th century found a way to live and work together, despite their contrasting cultures and political systems. But Russia is still the country that tried to expand into Turkey many times over the centuries. In the early 1950s, under Stalin, the USSR was still actually demanding territory from Turkey — a move that propelled Turkey into the Western alliance. For Russia now to have a significant military presence south of Turkey in Syria is a far-reaching and potentially alarming change in the geostrategic balance. Vastly more frustrating for Ankara, however, was the impact of Russian intervention on Turkey's drive to help overthrow Al-Assad and replace him with a government formed by the Syrian opposition. Active Russian backing means Al-Assad's chances of survival in a rump Syrian state look much stronger. Ankara's allies in the Syrian opposition have suffered repeated attacks from Russian jets and even missiles. Specifically, Russian intervention blocks Turkish direct support to the Army of Conquest — a coalition of moderate and hardline opposition fighters in northern Syria. The prospect of creating a safe zone along a stretch of Syria south of its frontier with Turkey, and perhaps eventually turning this into a no-fly zone, has now receded. CLASH IN THE SKIES: However, what has really strained links between Turkey and Russia is the regular buzzing or harassment of Turkish planes in their country's airspace close to the Syrian border, either by Russian jets or those of the Syrian air force. These do not seem to have been casual mistakes: despite declarations of solidarity with Turkey by NATO, incidents have continued with Western observers saying that the violations are deliberate. The most recent was the reported buzzing of Turkish jets by Syrian planes on 11 October. Even if these incidents are routine blustering and rudeness by members of the Russian armed forces and their allies and not a serious formal threat — the explanation believed to be given privately by Moscow — they have caused a serious flaring-up of tension and warnings from Turkey's NATO allies. This has led to talk of cutting off some of the country's economic and investment links with the Russians, according to President Erdogan and some of his ministers, perhaps even the Akkuyu nuclear power plant. “There are other places Turkey could get gas and other countries that could build its first nuclear plant,” the president said 6 October. On the Russian side, prospects of going ahead with Turkish Stream may be fading, while Russia dealt a blow to Turkey's energy programme on 5 October by announcing that it might substantially reduce the enlargement of the Blue Stream pipeline, which already supplies one third of Turkey's natural gas. However, Daily Sabah, a pro-government paper, denies this claim. A reduction in bilateral trade would badly hurt both countries. Though Turkey's energy import needs probably make it more exposed, the Russian economy is vulnerable too. There seem to be voices on both sides arguing that business should go on as usual. On 10 October, Ali Riza Alaboyun, minister of energy in the pre-election government, dismissed suggestions that the Akkuyu deal could be cancelled. “There is not any problem between Turkey and Russia about the project,” Alaboyun said. From Russia too there have been calls not to allow energy and economic cooperation to falter. Still, relations between the two countries are at their worst in 60 years. If Russia supports not only Al-Assad but Syria's Kurds too, they will certainly worsen further. While Russia remains in Syria, full normalisation will be difficult if not impossible.