Micahel has been in the Marines since late 1941 through early 1945 and then takes off for college. Yet:

When Mike arrives at Vito's house the night of Vito's shooting, the novel states that the house was full of men he didn't know.

He noticed several other men in the corners of the room, but he didn't recognize them. "They were not of Clemenza's people."

After McCluskey hit him, how is it that Mike recognized (of all people) Clemenza's lawyer who accompanied the private detectives hired to guard Vito at the hospital?

Why would Vito have to arrange Mike's discharge when Mike was suffering from a "disabling" wound?

"Generosity. That was my first mistake."
"Experience must be our only guide; reason may mislead us."
"Instagram is Twitter for people who can't read."