In order to receive Battlemaster reward you need to complete following achievments:
Master of Alterac Valley
Master of Warsong Gulch
Master of Strand of the Ancients
Master of Arathi Basin
Master of Eye of the Storm
Master of Alterac Valley
Alterac Valley (AV) is a battleground in the continuing war between the Horde and the Alliance. Alterac Valley has its own entrances in the game world, found in northern Hillsbrad Foothills. The Alliance entrance is due north of Southshore, while the Horde entrance is north-east of Tarren Mill. However, as with all battlegrounds, players can also queue for Alterac Valley through the PvP interface. With up to40 players on each team in this battleground, Alterac Valley is one of the largest battlegrounds available.The goal in AV is to reduce the opposing faction's reinforcement count to 0. The most direct way to do this is to kill the enemy general, which will immediately drain all reinforcement points from the enemy and end the round. Other activities which reduce reinforcement points include killing enemy players, capturing towers/bunkers, and killing the enemy captain.
Master of Warsong Gulch
Warsong Gulch is a 10v10 capture the flag battleground. Each side tries to take the opponent flag and "cap" (score) it at their own base. You can only "cap" the flag if the enemy isn't carrying yours. The winner is the first team to achieve 3 caps, or the team with the most caps when the allotted time expires.
Master of Strand of the Ancients
This battleground consists of 3 walls which have to be destroyed to continue, capture points and a graveyard after each wall. The overall goal is to be the faster team to break through the last wall and capture the relic inside.
Master of Arathi Basin
The goal is to control locations on the map ("Resource Nodes"). While a node is controlled, it generates resources for your side, and the first side to gain 1,600 resources wins the contest.
Master of Eye of the Storm
To win Eye of the Storm you need to earn 1600 resources before the opposing team does. Earn resources by capturing and holding the bases around the battleground, as well as capturing the flag that spawns in the center of the battleground.
It's a very complicated and tiresome line of quests but in the end you'll get a lot of rewards.