The Swiss army knife is a popular device that is recognized all over the world. In Switzerland, there is a saying that every good Swiss citizen has one in his or her pocket. But the knife had poor beginnings. In the late nineteenth century, the Swiss army issued  its soldiers a gun that required a special screwdriver  to take it apart and clean it. At the same time, canned food was becoming common in the army. Swiss generals decided to issue each soldier a standard knife to serve both as a screwdriver and a can opener.  _ was a lifesaver for Swiss knife makers, who were struggling to compete with cheaper German imports. In 1884, Carl Elsener, head of the Swiss knife manufacturer(maker) Victorinox, seized that opportunity with both hands, and designed a soldier's knife that the army loved. It was a simple knife with one big blade , a can opener, and a screwdriver. A few years after the soldier's knife was issued, the "Schweizer Offizier Messer," or Swiss Officer's Knife, came on the market. Interestingly, the Officer's Knife was never given to those serving in the army. The Swiss army purchasers considered the new model with a corkscrew  for opening wine not "essential for survival," so officers had to buy this new model by themselves. But its special multi-functional design later launched  the knife as a global brand. After the Second World War, a great number of American soldiers were stationed in Europe. And as they could buy the Swiss army knife at shops on army bases, they bought huge quantities of them. However, it seems that "Schweizer Offizier Messer" was too difficult for them to say, so they just called it the Swiss army knife, and that is the name it is now known by all over the world. What is the main purpose of the passage?
To explain the origin of the Swiss army knife. To introduce the functions of the Swiss army knife. To emphasize the importance of the Swiss army knife. To tell a story about the designer of the Swiss army knife.