The ease of traversing the frontier was noted by the exiled Leander, whose brother more than once crossed it without hindrance. The border had been determined by a treaty (pacta) between Athanagild and Justinian I, but the date of the treaty is still debated. It may have been part of the initial conditions of Byzantine assistance in 551 or 552 or it may have been a product of the war between Goth and Roman in 555 or later.