When Lee Kuan Yew died Monday at age 91, the founding father of Singapore did not leave just his legacy as the prime minister whose authoritarian policies shaped a backwater British colony into the world’s fourth-wealthiest nation. He also left Singaporeans with one of the most formidable armies in the world. The tiny island state of 5.4 million, with a land area far smaller than New York City’s, has more fighter jets than Spain, Poland or Sweden. Its army has as many tanks as Italy, which is more than 400 times the size. Its navy boasts the only stealthy ships...