All out war by Turkey on the Assad regime in Syria would be counterproductive, especially as it would almost certain to be perceived by the Syrian population as an attempt to revive the Turkish Ottoman Empire. That would result in a 3 way war between Turkey, the rebels, and the Assad regime.The second and equally important point is the role of Moscow if & when all-out war invoked by Turkey alone. Here Turkey needs full military backing (not the mare words of alliance & partnership) of NATO to counter Russians.
Russia does not have an effective means of intervening militarily in the event of Turkey taking any actions. Assuming no direct support for Turkey by NATO:
- Any attack by Russia on Turkey would result in the immediate loss of the access between the Mediterranean Sea and the Black Sea for Russian shipping and goods. This would have dramatic impact on the Russian economy, and the loss of oil exports would be compounded by Europe shifting its long term energy focus from Russia to Africa as a result.
- The only land routes to Turkey go through Georgia and Azerbaijan, neither of whom are on good terms with Russia, and offer good terrain for the defenders in those countries and Turkey.
- Naval attacks by Russia would prompt a massive naval response by NATO if it threatens the tanker traffic across the Black Sea, independent of any Turkish request for support. The Russians do not have an advantage in ships or firepower versus the Turkish navy, and Turkey controls the only means to reinforce.
- Russian air attacks across the Black Sea would face the largest non-USA air force in NATO, with over 200 F-16 fighters. Russia can exceed this only by stripping fighters other fronts.
- Russian naval power in the Mediterranean Sea will be cut off from its bases on the Black Sea in event of a conflict with Turkey. The Russian base at Tartus can offer only limited logistical support, and is vulnerable to Turkish attack.