With thousands of heavily armed Russian troops occupying this perennially embattled peninsula, an overwhelming majority of crimeans voted on sunday to secede from ukraine and join russia, resolutely carrying out a public referendum that western leaders had declared illegal and vowed to punish with economic sanctions. The outcome, in a region that shares a language and centuries of history with russia, was a foregone conclusion even before exit polls showed more than 93 percent of voters favoring secession.