- The Naval pilot-turned-politician survived over five years as a prisoner of war in Vietnam
- McCain asked the Pentagon for more information on the current and future fight against ISIS
"As a young military officer, I bore witness to the failed policy of gradual escalation that ultimately led to our nation's defeat in the Vietnam War," McCain, chairman of the Senate Armed Services Committee, wrote in a letter sent to Defense Secretary Ash Carter.
The Naval pilot-turned-politician survived over five years as a prisoner of war in Vietnam.
McCain said that he fears the nation's current strategy of "grudging incrementalism in the war against the Islamic State risks another slow, grinding failure for our nation."
In the letter, the Arizona Republican asserted that conversations he has had with military commanders confirm for him that the military's actions have shifted from "considering what it will take to win" to "what they will be allowed to do by the administration."
In response to a request for comment, Pentagon spokesman Matthew Allen told CNN, "The Department has received Senator McCain's letter and will respond directly as appropriate."
McCain concluded his letter with several questions seeking more information on the current and future fight against ISIS, also known as ISIL, in Iraq, Syria and Libya.
As the Senate Armed Services Committee weighs the Defense Department's 2017 budget request, McCain said he and his committee "must have full insight into the scale and scope of U.S. military operations against ISIL."
McCain worried that members of military "will pay the price."
"This," McCain said, "is unacceptable."