While brainstorming occasionally trying to come up with something interesting sounding, yet short and practical, and different enough from the horde's battle cry, I came up with "Honor the Blood". I am sure many will hate the idea, but post here with your own instead of trolling.
Background story (a very basic, non-detailed storyline):
The alliance are in turmoil, and they are breaking slowly apart. The leaders don't seem to be able to compromise in the direction they want the alliance to go. An impending dispersion of the alliance is imminent. Velen (he seems the most logical, but does not even need to be an alliance boss) gathers the alliance leaders, using reasoning, diplomatic solutions, and urging the need to stay together, rather than splitting into smaller, weaker kingdoms and letting the horde dismantle each race one at a time.
After gathering all the alliance leaders together at a vieled location in a last ditch effort to try to reunite the alliance, Velen finally convinces (someone with a more creative imagination than I will have to come up with these details) his peers to commit to a blood pact. Essentially binding dwarf, gnome, human, draenai, and elf together in a much deeper, more meaningful manner than before.
And "honor the blood" is born