his first story, and he was quickly acknowledged as a leader of the new movement toward "social" science fiction. In California he hosted the Mañana Literary Society, a 1940–41 series of informal gatherings of new authors. He was the guest of honor at Denvention, the 1941 Worldcon, held in Denver. During World War II, Heinlein was employed by the Navy as a civilian aeronautical engineer at the Navy Aircraft Materials Center at the Philadelphia Naval Shipyard in Pennsylvania. Heinlein recruited Isaac Asimov and L. Sprague de Camp to also work there. While at the Philadelphia Naval Shipyards, Asimov, Heinlein, and de Camp brainstormed unconventional approaches to kamikaze attacks, such as using sound to detect approaching planes. As the war wound down in 1945, Heinlein began to re-evaluate his career. The atomic bombings of Hiroshima and Nagasaki, along with the outbreak of the Cold War, galvanized him to write nonfiction on political topics. In addition, he wanted to break into better-paying markets. He published four influential short stories for The Saturday Evening Post magazine, leading off, in February 1947, with "The Green Hills of Earth". That made him the first science fiction writer to break out of the "pulp ghetto". In 1950, the movie Destination Moon—the documentary-like film for which he had written the story and scenario, co-written the script, and invented many of the effects—won an Academy Award for special effects. Also, he embarked on a series of juvenile novels for the Charles Scribner's Sons publishing company that went from 1947 through 1959, at the rate of one book each autumn, in time for Christmas presents to teenagers. He also wrote for Boys' Life in 1952. Heinlein had used topical materials throughout his juvenile series beginning in 1947, but in 1958 he interrupted work on The Heretic (the working title of Stranger in a Strange Land) to write and publish a book exploring ideas of civic virtue, initially serialized as Starship Soldiers. In 1959, his novel (now entitled Starship Troopers) was considered by the editors and owners of Scribner's to be too controversial for one of its prestige lines, and it was rejected. Heinlein found another publisher (Putnam), feeling himself released from the constraints of writing novels for children. He had told an interviewer that he did not want to do stories that merely added to categories defined by other works. Rather he wanted to do his own work, stating