<span style="color: #222222;">Two Russian warships transited the Bosphorus en route to the Black Sea today and 15 smaller vessels completed a transfer to the sea as Moscow beefs up its naval presence at a time of tense relations with the West and Ukraine.</span><br />'' <br />'' <span style="color: #222222;">The reinforcement coincides with a huge build-up of Russian troops near Ukraine, something Moscow calls a temporary defensive exercise, and follows an escalation in fighting in eastern Ukraine between Russian-backed separatists and Ukrainian government forces.</span><br />'' <br />'' <span style="color: #222222;">Moscow expelled 10 American diplomats yesterday in retaliation for the expulsion of the same number of Russian diplomats from the United States over alleged malign activity. </span><br />''  <br />