The main method for obtaining Nazjatar Battle Commendation is to participate in the new PvP event in Nazjatar, called Battle for Nazjatar. This is a zone-wide battle where each faction fights to control five different controls points, called Tidal Conflux, Alathi Spire, Thoras'tal Spire, Zin-Azshari, and Lemor'athra Spire. Each tick where your faction controls one of these points award a point to your faction.
Each game lasts until one faction has 1,000 points, or it ends 45 minutes after it begun. It seems like most games will end much earlier than 45 minutes though. A new game begins shortly after the previous one ended, so it's pretty much always possible to participate in the battle event.
If your faction wins the battle, you will be awarded 3 x Nazjatar Battle Commendations + 100 Conquest. If you lose, you only get a single Nazjatar Battle Commendation plus 25 Conquest points.
In addition to participating in the Battle for Nazjatar you can get extra Nazjatar Battle Commendations by completing PvP World Quests in Nazjatar, but that is limited to once per day.
As you might have guessed, you will need to have War Mode turned on to be able to participate in the Battle for Nazjatar, so you won't get any Nazjatar Battle Commendations without War mode on.
Idle with War Mode on to get them passivelyIt seems like everyone who are currently in Nazjatar get awarded with Nazjatar Battle Commendations even if they are doing other activities like World Quests or just grinding mobs, so you might not need to actively participate in the battle to get the rewards. However, you will still need to have War Mode enabled to get these.
The Nazjatar Battle Commendations can be used to buy items from Crafticus Mindbender (Alliance) and Dazzerian (Horde), and they sell the following items:
All items purchasable with Nazjatar Battle Commendation
- Alliance War Banner / Horde War Banner (Toy) - 10 Nazjatar Battle Commendations.
- Alliance War Standard / Horde War Standard (Toy) - 30 Nazjatar Battle Commendations.
- Inkscale Deepseeker (mount) - 150 Nazjatar Battle Commendations.
- Engine of Ceaseless Progress (Blue/Rare Essence) - 20 Nazjatar Battle Commendations.
- Engine of Ceaseless Progress (Green/Uncommon Essence) - 5 Nazjatar Battle Commendations.
- Engine of Ceaseless Progress (Purple/Epic Essence) - 50 Nazjatar Battle Commendations.