The myth that Afghanistan is our longest war
The longest open conflicts involving the United States were the 19th century Indian wars during the westward expansion of the country. I recognize that these wars offend modern sensibilities, but my argument here is about length, not justification.
Armistice is Dangerous
We mark the end of World War I on Veterans Day, formerly Armistice Day, commemorating the military agreement to end combat. But the war didn't end until the Paris Peace Conference adjourned, in January 1920. Ending combat does not end the state of war. By that principle, the United States is currently in a state of war with nine countries: Afghanistan, China, Cuba, Iran, Iraq, Libya, North Korea, Somalia, and Russia; seven of these conflicts are inactive.
The Struggle for Civilization
Our enemies started their War Against Civilization, in the 18th century, not the 21st century. It doesn't help our understanding that this war against civilization is so outside of our modern sensibilities. To make sense of it, we have to consider the enemies' world as "inside the looking glass" -- as puzzling to us as the Red Queen was to Lewis Carroll's Alice.