Complex sentence: As other nations, which had initially all been sharing their data and analysis, translate their versions of the message, they close down communication with each other, with some of them starting to scramble their military, believing that the message indicates a threat.
Split into simpler sentences: As other nations, which had initially all been sharing their data and analysis, translate their versions of the message, they close down communication with each other. Some of them start to scramble their military, believing that the message indicates a threat.