This is the first in a two-day series exploring the South Korean population’s perception of the U.S. military presence. SEOUL — When the Korea Military Academy asked its incoming cadets in 2004 to name South Korea’s main enemy, they were shocked at the answer: 34 percent said the United States while only 33 percent said North Korea. The country’s top military leaders asked that question of the 250 cadets — among the smartest university students in the nation — because they wanted to know if a 2-year-old surge of anti-Americanism had influenced the future military officers, Kim Chul-woo said. He...