The sharpest exchange in the Oct. 22 presidential debate centered on the size of America’s Navy. Mitt Romney, the Republican nominee and former Massachusetts governor, highlighted the shrinking size of the fleet, noting it was now the smallest it has been since World War I, a point he has brought up often on the stump. That brought a retort from his opponent. “You mentioned the Navy, for example, and that we have fewer ships than we did in 1916,” President Obama replied in the final debate, which focused on foreign policy and during which the president strove to paint his…