Lamb was born in Alpine, New Jersey. He attended Columbia University, where his interest in the peoples and history of Asia began. Lamb's tutors at Columbia included Carl Van Doren and John Erskine. Lamb built a career with his writing from an early age. He got his start in the pulp magazines, quickly moving to the prestigious Adventure magazine, his primary fiction outlet for nineteen years. In 1927 he wrote a biography of Genghis Khan, and following on its success turned more and more to the writing of non-fiction, penning numerous biographies and popular history books until his death in 1962. The success of Lamb's two volume history of the Crusades led to his discovery by Cecil B. DeMille, who employed Lamb as a technical advisor on a related movie, The Crusades, and used him as a screenwriter on many other DeMille movies thereafter. Lamb spoke French, Latin, Persian, and Arabic, and, by his own account, a smattering of Manchu-Tartar.
Although Harold Lamb wrote short stories for a variety of magazines between 1917 and the early 1960s, and wrote several novels, his best known and most reprinted fiction is that which he wrote for Adventure magazine between 1917 and 1936. The editor of Adventure, Arthur Sullivant Hoffman, praised Lamb's writing ability, describing him as "always the scholar first, the good fictionist second". The majority of Harold Lamb's work for Adventure was historical fiction, and can be thematically divided into three broad categories of tales:
- Stories Featuring Cossacks
- Stories Featuring Crusaders
- Stories with Asian or Middle-Eastern Protagonists
In a Lamb story, honor and loyalty to one's comrades-in-arms were more important than cultural identity, although often his protagonists ended up risking their lives to protect the cultures that had spurned them. Those holding positions of authority are almost universally depicted as being corrupted by their own power or consumed with greed, be they Russian boyars or Buddhist priests, and merchants are almost always shown as placing their own desire for coin above the well-being of their fellow men. Loyalty, wisdom, and religious piety is shown again and again in these stories to lie more securely in the hands of Lamb's common folk.
While female characters occasionally played the familiar role of damsel in distress in these stories, Lamb more typically depicted his women as courageous, independent, and more shrewd than their male counterparts. Their motives and true loyalties, though, remained mysterious to Lamb's male characters, and their unknowable nature is frequently the source of plot tension.
Lamb was never a formula plotter, and his stories often turned upon surprising developments arising from character conflict. The bulk of his Crusader, Asian, and Middle-Eastern stories (as well as the latter stories of Khlit the Cossack) were written in the latter portion of his pulp magazine years, and demonstrate a growing command of prose tools; the more frequent use, for example, of poetic metaphor in his descrip.