Pete, in the novel law enforcement starts cracking down on all of the families' activities as a result of the McClusky murder and they demanded that the Corleones give up the murderers. Eventually, Sonny realizes that the Corleones are overmatched.

What's interesting to me about that is that the war apparently was costing so many lives that the Families' counter-blows declined and then eventually ceased. Sonny was jubilant and said he would pour it on. That was the root of the deception by the families; make Sonny think he was winning, get him to be careless, and then strike. So, what if Sonny takes Tom's advice and ceases his attacks on the families and even sues for peace? I also question what the families were trying to accomplish by deceiving Sonny? Was it purely to end the killing by killing Sonny? Certainly, they could have accomplished that by suing for peace. For me, that's where the murkiness comes in.