Schutzstaffel served Adolf Hitler; this was condensed into one character in the form of Vader. Stormtroopers borrow the name of World War I German "shock" troopers. Imperial officers wear uniforms resembling those of German forces during World War II, and political and security officers resemble the black-clad SS down to the stylized silver death's head on their caps. World War II terms were used for names in the films; e.g. the planets Kessel (a term that refers to a group of encircled forces) and Hoth (after a German general who served on the snow-laden Eastern Front). Shots of the commanders looking through AT-AT walker viewscreens in The Empire Strikes Back resemble tank interiors, and space battles in the original film were based on World War I and World War II dogfights. Palpatine being a chancellor before becoming the Emperor in the prequel trilogy alludes to Hitler's role before appointing himself Führer. Lucas has also drawn parallels to historical dictators such as Julius Caesar, Napoleon Bonaparte, and politicians like Richard Nixon. The Great Jedi Purge mirrors the events of the Night of the Long Knives. The corruption of the Galactic Republic is modeled after the fall of the democratic Roman Republic and the formation of an empire. On the inspiration for the First Order formed "from the ashes of the Empire", The Force Awakens director J. J. Abrams spoke of conversations the writers had about how the Nazis could have escaped to Argentina after WWII and "started working together again." Cultural impact The Star Wars saga has had a significant impact on popular culture, with references to its fictional universe deeply embedded in everyday life. Phrases like "evil empire" and "May the Force be with you" have become part of the popular lexicon. The first Star Wars film in 1977 was a cultural unifier, enjoyed by a wide spectrum of people. The film can be said to have helped launch the science-fiction boom of the late 1970s and early 1980s, making science-fiction films a mainstream genre. The widespread impact made it a prime target for parody works and homages, with popular examples including Hardware Wars, Spaceballs, The Family Guy Trilogy and Robot Chicken: Star Wars. In 1989, the Library of Congress selected the original Star Wars film for preservation in the U.S. National Film Registry, as being "culturally, historically, or aesthetically significant." The Empire Strikes Back was selected in 2010, and