The Legion of the Wall is the elite military formation and standing army of the kingdom of Ghealdan. It is named for Garen's Wall, the immense ridgeline on the northeastern edge of the country that formed its major defensive fortification for the entirety of its existence and even prior, when the kingdom of Dhowlan used the wall as a defensive bulwark in its wars with Farashelle to the north.
The Legion was the only major, professional military body in a small country whose main martial strength lay in levies. The Legion provided the core to a levy army raised in times of crisis, acted as both the bodyguard to the King or Queen, and also policed the capital city of Jehannah.
The Legion suffered severe losses in the battles against the false Dragon Logain Ablar and the alleged self-proclaimed Prophet of the Dragon, Masema Dagar. It was dispersed on Masema's orders. Ghealdan's Crown High Council refused to let Queen Alliandre Maritha Kigarin reconstitute the Legion after Masema moved into Amadicia, feeling that the absence of the Legion gave greater influence and power to them. Despite this point, Alliandre had begun to reconstitute the Legion, appointing Gerard Arganda as First Captain, prior to her abduction by the Shaido Aiel. 
After Alliandre was captured by the Shaido, her Liege Lord Perrin Aybara embarked on a mission to rescue her and his wife, Faile Bashere. This campaign culminated at the Battle of Malden, by which time the Ghealdanin contingent of his forces had grown confident enough to openly name themselves the Legion of the Wall once more. The Crown High Council's reaction to this news remains to be seen.