YOKOSUKA, Kanagawa Pref. — When the USS Charlotte arrived for a recent port call, some of its crew were surely relieved to find themselves in Japan, traditionally a smoker's haven.

As if life on a submarine wasn't already stressful enough, with its cramped quarters, long work hours and weeks at sea, thousands of smokers in the U.S. Navy's submarine fleet recently got an unwelcome ultimatum from Uncle Sam.

As of last month, all submarines in the U.S. Navy are officially smoke free — and it's been a tense transition.