OF COURSE Sollozzo woudn't try to kill Vito without support. That was part of Barzini's plan. As night follows day, Barzini knew that, when Vito rejected Sollozzo's offer, he'd come back to Barzini with a plan to kill Vito--and begging for his support. Thats when Barzini began tightening the screws: "Well, you're gonna have to give me something if you want my support in killing Vito." When the hit attempt failed, Barzini tightened the screws again, as I said.