After Vito was shot, Tom urged Sonny to make a deal with Solozzo. Here's the relevant dialog:
SONNY: Well, Tom -- you're consiglieri, now what do we do if the old man dies, God forbid.
TOM: If we lose the old man we lose our political contacts and half our strength. The other New York Families might wind up supporting Sollozzo just to avoid a long -- destructive war. This is almost 1946 --
-- nobody wants bloodshed anymore. If your father dies, (then) you make the deal, Sonny.
Do you think Sonny would have made the deal if Vito had died?