sentence1: At 10 : 59 AM the last naval element of the 2nd Marine Battalion left the zone and the last helicopter landed at 12 : 15 on the USS " Okinawa " .
sentence2: At 10 : 59 , the last element of 2nd Battalion 4th Marines left the zone and the last marine helicopter landed on the USS " Okinawa " at 12 : 15 .