In the spring of 1967, Egypt’s president, Gamal Abdel Nasser, lamented to the U.S. ambassador in Cairo that the war in Yemen had become his “Vietnam.” He subsequently explained to an Egyptian historian how the conflict spiraled out of control: “I sent a company to Yemen and ended up reinforcing it with 70,000 troops.”

Over the course of the five-year war, from 1962 to 1967, Nasser lost more than 10,000 men, squandered billions of dollars, and painted himself into a diplomatic corner from which the only way out was through war with Israel. As Nasser himself would realize by the war’s end, Yemen was to Egypt what Vietnam was to the United States — and what Afghanistan was to the Soviet Union, what Algeria is to France, and what Lebanon is to Israel.

Not surprisingly, the predominant takeaway for Egyptians was “never again.” Never again would they send their boys to fight for a dubious cause on a remote battlefield.

Never again would they waste their modern army to build a nation where there was none. Never again would they set foot in Yemen.

Perhaps “never” is too strong a word. A half-century later, President Abdel Fattah al-Sisi is once again contemplating the dispatch of ground forces to Yemen, this time in support of the Saudi-led assault on the Houthis. Sisi has already committed Egypt’s navy and air force to the military campaign and has said that ground forces would be sent “if necessary.” As the Saudis, the Egyptians, and their allies hover on the brink of another military adventure in Yemen, history offers some stark lessons of the challenges that may block their road to victory.