Jihad: Final Reckoning has an entry in the Jihad timeline on page 61 the entry for 31 March 3081 indicating that the 49th Shadow Division intercepts and destroys the Nightwatchmen over Andiron. I can't find another reference to the Nightwatchmen other than the Nightwatchmen being a nickname for the WOB 25th Division, which Jihad: Final Reckoning indicates were destroyed on Terra in 3078.
Was it the 25th Division that was destroyed over Andiron, or does the name "the Nightwatchmen" refer to another unit?
