Differences between 1st edition and 2nd edition:
After Nexus, the publisher of the 1st edition, filed for bankruptcy, War of the Ring was picked up by Ares Games, and the designers used the opportunity of the new print run to release a 2nd edition that incorporates a few simple rule and card changes to address a few game balance and integrity issues that had been exploited by experienced players.
Note: It is not recommended to use the Twilight of the Third Age 1st-edition expansion module in the War of the Ring: Battles of the Third Age with the 2nd edition, because both it and the 2nd edition make the Free Peoples slightly stronger relative to the 1st-edition base game (which is generally regarded as slightly favoring the Shadow player), hence making the Free Peoples player too strong. Instead, Ares Games will be releasing a whole new arc of expansions that is compatible with the 2nd edition and introduces new ideas, starting with War of the Ring: Lords of Middle-Earth.
