America continues to struggle over the war in Afghanistan. About 190 local business and political leaders got some insight last week when the World Affairs Council of Orange County (California) hosted Ronald E. Newman, the U.S. ambassador to that country from 2005 to 2007. He is the author of the recent book, “The Other War: Winning and Losing in Afghanistan.”

He said America needs to continue its military forces in that country — recently increased to near 100,000, triple the number when President Barack Obama took office. Mr. Newman said the “massive instability” in that part of the world, including Afghanistan’s neighbors Iran and Pakistan, “makes a strong case to persevere.”

He said it was a mistake for President Obama to announce that troops would be withdrawn beginning in July 2011. Since then, he said, the president was right to back away from that deadline. What is needed, Mr. Newman said, is stable policies on which the government of Afghan President Hamid Karzai can build a more solid regime. If America pulls out, the entire region could suffer instability.

“The cause we are fighting is worth a great deal of sacrifice,” Mr. Newman said. People need “the patience and the resolution to keep backing the effort.” This sounds to us like the old “domino theory” on the Vietnam War, in which, if South Vietnam was conquered by North Vietnam and became communist, the rest of Asia might also become communist. That didn’t happen.

Unfortunately, Mr. Newman didn’t discuss the huge cost this too-long war, and the related war in Iraq, have taken on American lives, the economy and the Constitution. Our longest declared war was World War II, at less than four years. By contrast, with presidents starting wars on their own, as in this case, the result has been a series of long, expensive wars that have divided the country: Vietnam (eight years), Iraq (seven years so far) and Afghanistan (nine years and counting, the longest in our history).

If this war is so important, supporters should follow the Constitution and get Congress to declare war to do the job right. Otherwise, it’s long past time to develop the exit strategy.