Geopolitics makes for strange bedfellows, and at times countries with disparate politics or cultures still form alliances that make strategic sense. Both Ukraine and Turkey have been engaged in indirect military combat operations against Russia and have seen relations with Moscow deteriorate as a result.
In addition to their common Russian enemy, Ukraine and Turkey share geographic commonalities. Each is located on the Black Sea, which also happens to be the site of one of Russia's largest military buildups over the past two years. In response to the Euromaidan uprising in Kiev — which set Ukraine and Russia on a collision course — Russia annexed Crimea, expelled Ukrainian military forces from the peninsula and beefed up its own military presence there. Russia's annexation of Crimea put both nations at a strategic disadvantage: It forced Kiev to relocate naval assets from its major base in Sevastopol, and countered Ankara’s substantial naval presence on the Black Sea controlled via the Bosporus.
There are other security measures that Turkey and Ukraine could take to strengthen their united front against Russia. The joint military exercises already being conducted under NATO in the Black Sea could be expanded and made more frequent. Another area of partnership outside the military realm could be the mobilization of the Crimean Tatars, an ethnically Turkic group that, prior to Russia's annexation of Crimea, made up about 10 percent of the peninsula's population.
Still, any military cooperation between Ukraine and Turkey is likely to be checked by each country’s need to allocate attention to respective conflicts in eastern Ukraine and Syria, which are entirely distinct in terms of both geography and tactics. Turkey is also burdened by the Kurdish insurgency in its southeast. However, Kiev and Ankara's shared desire to counter Moscow and weaken Russia's position in the conflicts is compelling enough reason for Ukraine and Turkey to align defensively with each other, at least for now.