The Corleone Family has the power

Tom Hagen looked him directly in the eye. "Sonny, sure you can outfight him. The Corleone Family has the power. You have Clemenza and Tessio here and they can muster a thousand men if it comes to an all-out war. But at the end there will be a shambles over the whole East Coast and all the other Families will blame the Corleones. We'll make a lot of enemies. And that's something your father never believed in."
 Michael, watching Sonny, thought he took this well. But then Sonny said to Hagen, "What if the old man dies, what do you advise then, Consigliere?"
  Hagen said quietly, "I know you won't do it, but I would advise you to make a real deal with Sollozzo on the drugs. Without your father's political contacts and personal influence the Corleone Family loses half its strength. Without your father, the other New York Families might wind up supporting the Tattaglias and Sollozzo just to make sure there isn't a long destructive war. If your father dies, make the deal. Then wait and see."
 Sonny was white-faced with anger. "That's easy for you to say, it's not your father they killed."
  Hagen said quickly and proudly, "I was as good a son to him as you or Mike, maybe better. I'm giving you a professional opinion. Personally I want to kill all those bastards." The emotion in his voice shamed Sonny, who said, "Oh, Christ, Tom, I didn't mean it that way." But he had, really. Blood was blood and nothing else was its equal.
  Sonny brooded for a moment as the others waited in embarrassed silence. Then he sighed and spoke quietly. "OK, we'll sit tight until the old man can give us the lead. But, Tom, I want you to stay inside the mall, too. Don't take any chances. Mike, you be careful, though I don't think. even Sollozzo would bring personal family into the war. Everybody would be against him then. But be careful. Tessio, you hold your people in reserve but have them nosing around the city. Clemenza, after you settle the Paulie Gatto thing, you move your men into the house and the mall to replace Tessio's people. Tessio, you keep your men at the hospital, though. Tom, start negotiation over the phone or by messenger with Sollozzo and the Tattaglias the first thing in the morning. Mike, tomorrow you take a couple of Clemenza's people and go to Luca's house and wait for him to show up or find out where the hell he is. That crazy bastard might be going after Sollozzo right now if he's heard the news. I can't believe he'd ever go against his Don, no matter what the Turk offered him.