"I was never able to convince myself that there was a cost-free alternative course, as from 1961, or that any of the different strategies since proposed, especially those involving stronger military action, would have made sense"

William P. Bundy is describing the Vietnam War, which began in 1961. He is saying that he was never ever able to find a strategy that would not have a cost, either in regards to money or lives. He is likewise saying that any of the techniques proposed ever since, specifically those including more powerful military action, would not have actually made sense. He is suggesting that the war was a mistake which the expense of it was too high. He is recommending that the war must have been prevented, which any efforts to escalate it would have been much more expensive. His words are a tip of the disaster of the Vietnam War and the disastrous repercussions it had on a lot of people.