For work weary Americans , Miami , Florida , has always been the ideal spot for a winter vacation . War put a temporary stopper on the vacation trade for in 1942 virtually all the big hotels were taken over by the Army . But this year the Army turned two thirds of them back for civilian use , and with the flood gates open , Miami is enjoying the biggest boom in its history . What this adds up to is a great strain on housing accomodations , a windfall for Miami tradesmen and some much needed , though a bit crowded , relaxation for war working Americans