Seventy years after the Battle of Okinawa, Yoshiko Shimabukuro still has terrifying nightmares of watching friends and Japanese soldiers die as they hid in caves to escape fierce US shelling.

One of 222 female students mobilized to serve in a battlefield nursing unit for the Imperial Army in March 1945, she also suffers deep pangs of guilt for surviving the war while many of her classmates perished in the hell holes that served as military hospitals on the island's southern tip.

"We only had basic training in how to put on bandages, but the wounded soldiers they brought in were beyond help," Shimabukuro said, ahead of a ceremony on Tuesday to mark the 70th anniversary of the battle's end.