I think they did know it was Pop's birthday. I think they were in league with Barzini. They figured that Vito would be so enraged that he would move his operations out west so that he could retaliate against the Japanese Empire. That would leave Barzini free to operate in the east with the cooperation of the Nazis. Thus re-establishing the German Alliance with "The Turks" in WWI
"Io sono stanco, sono imbigliato, and I wan't everyone here to know, there ain't gonna be no trouble from me..Don Corleone..Cicc' a port!"
"I stood in the courtroom like a fool."
"I am Constanza: Lord of the idiots."
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