For some reason, For Honor will require you to be online all the time even though it includes a single player campaign.
A NeoGaf user contacted an Ubisoft representative and they said: “We can confirm that For Honor is an always online experience. Some elements of progression, which is hosted online, are shared across story and multiplayer modes. Players will need to be connected to the Internet at all times to play For Honor.”
Ubisoft has been the only publisher to mandate always online for many video games lately. First there was The Crew, Rainbow Six Siege, The Division, Steep and now For Honor.
Ubisoft did promise the game would be playable offline a few months ago, but it looks like they changed their minds. At least Watch Dogs 2 is playable offline. This might be a sign that Ghost Recon: Wildlands will be always online too…