The most basic examples of long weapons include the quarterstaff and the spear, though numerous, far more sophisticated variants exist, such as the halberd, the Guandao, the long mace, the bec de corbin, and the corseque. Because of their long range, polearms can be employed to effectively keep adversaries at bay, and historically, they have served in dedicated defensive roles such as on the battlefield against cavalry. Seekers, guards specialized in the use of long weapons, were a mainstay of professional armies before firearms rendered mêlée weapons obsolete, and these soldiers were often deployed as guardsmen of entrances and exits.