@glent @mattblaze @SteveBellovin @karlauerbach found this brief article on the history of the security of undersea cables (telegraphic onwards) interesting - more on the who and where rather than the outcomes - eg it mentions the UK cutting German telegraph cables on the outbreak of WW1 but not the Zimmerman telegram. https://www.maritimefoundation.uk/publications/maritime-2023/the-security-of-subsea-cables-an-enduring-naval-challenge/