What happened
In a televised address, Kennedy disclosed the Soviet missile deployment and demanded its removal. He also spoke with British Prime Minister Harold Macmillan. The advisory group was formally constituted as ExComm. An intensely secret crisis was now a matter of public knowledge across the world.
Sources for this passage: [1]The audience becomes worldwide
Kennedy briefed congressional leaders and senior officials, and spoke to former presidents and Macmillan before his evening address. Rusk informed Dobrynin shortly before the broadcast. The speech at 7 p.m. Eastern Daylight Time made the secret deployment and the American response a public international crisis.
In his telephone conversation with Macmillan, Kennedy explained the concern that stronger action in Cuba could invite a Soviet move against Berlin. He also promised to speak with the Prime Minister again before an invasion. The American memorandum mostly records Kennedy’s side of the call, so it cannot be read as a complete transcript of Macmillan’s replies.
Sources for this passage: [1] [2]