Lamb was born in Alpine, New Jersey to Eliza Rollinson and Frederick Lamb. He was the nephew of the architect Charles Rollinson Lamb. 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. He later got a Guggenheim Fellowship for twelve months, starting on April 1, 1929.
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 in Rochester, N.Y. 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 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:
Lamb's prose was direct and fast-paced, in stark contrast to that of many other contemporary adventure writers. His stories were well-researched and rooted in their time, often featuring real historical characters, but set in places unfamiliar and exotic to most of the western audience reading his fiction. While his adventure stories had familiar tropes such as tyrannical rulers and scheming priests, he avoided the simplistic depiction of foreign or unfamiliar cultures as evil; many of his heroes were Mongolian, Indian, Russian, or Muslim. Most of his protagonists were outsiders or outcasts apart from civilization, and all but a very few were skilled swordsmen and warriors.
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 description.
By far the largest number of these tales were short stories, novellas, and novels of Cossacks wandering the Asian steppes during the late 16th and early 17th century, all but a half-dozen featuring a set of allied characters. Two early books (Kirdy and White Falcon) reprinted the longest of these Cossack adventures, and two later books (The Curved Saber and The Mighty Manslayer) reprinted fourteen of the short stories; the four large Steppes volumes published by The University of Nebraska Press present all of Lamb's Cossack tales in their chronological order.
The most famous of these Cossack characters is Khlit, a greybearded veteran who survives as often by his wiles as his swordarm; he is a featured character in eighteen of the Cossack adventures and appears in a nineteenth. He chooses to wander Asia rather than face forced "Cossack retirement" in a Russian monastery, and launches into an odyssey that takes him to Mongolia, China, and Afghanistan. He comes to befriend and rely upon folk he has been raised to despise, and briefly rises to leadership of a Tartar tribe before he wanders further south. His greatest friend proves to be the swashbuckling Muslim swordsman, Abdul Dost, whom he aids in raising a rebellion against the Moghul emperor in Afghanistan. In later stories Khlit returns as a secondary character, an aged advisor to both his adventurous grandson, Kirdy, and other Cossack heroes featured in separate stories.
Unlike Lamb's Cossack stories, only a handful of his Crusader stories are inter-related. Two novelettes feature the young knight, Nial O'Gordon, and three short novels are centered around Sir Hugh of Taranto, who rediscovers the sword of Roland, Durandal. Durandal, published in 1931, reprinted all three novels of Sir Hugh with new linking material. Grant books' Durandal and The Sea of Ravens each reprint a single of these three novels.
While Lamb's Crusaders sometimes battle against their traditional Muslim foes, the majority of these tales feature forays into deeper Asia.
All of Lamb's Crusader stories have been collected in the 2009 Bison volume Swords from the West except for Durandal, The Sea of Ravens, and the forthcoming Rusudan, all from Donald M. Grant Co. Related stories with occasional Crusaders are collected in Swords from the Desert (Bison, 2009).
Lamb also wrote a variety of stories featuring or narrated by Muslim, Mongol, or Chinese protagonists, set for the most part during the late 16th and early 17th centuries. "The Three Palladins" is a story of young Genghis Khan, told mostly from the viewpoint of one of his boyhood comrades, a Chinese prince.
Lamb wrote several novels which were almost in the nature of dramatized biographies. Very little was invented beyond known history.
Lamb produced several fantasy novels featuring lost worlds. These included Marching Sands, about a lost city of Crusaders in the Gobi Desert. A Garden to the Eastward features a hidden tribe living in a volcano in Kurdistan.
Robert E. Howard described Lamb as one of his "favourite writers". Cecelia Holland has described Lamb as "a master of pace, he had a gift also for the quick glimpse of a landscape that throws everything into perspective", and has praised Lamb's plotting and action writing.