http://en.wikipedia.org/wiki/True_Cross
In 614 the Sassanid Emperor Khosrau II ("Chosroes") removed the part of the cross as a trophy, when he captured Jerusalem. Thirteen years later, in 628, the Byzantine Emperor Heraclius defeated Khosrau and retook the relic, which he at first placed in Constantinople, and later took back to Jerusalem in March 21, 630. [8] Around 1009, Christians in Jerusalem hid the part of the cross and it remained hidden until it was rediscovered during the First Crusade, on August 5, 1099, by Arnulf Malecorne, the first Latin Patriarch of Jerusalem, conveniently at a moment when a morale boost was needed. The relic that Arnulf discovered was a small fragment of wood embedded in a golden cross, and it became the most sacred relic of the Latin Kingdom of Jerusalem, with none of the controversy that had followed their discovery of the Holy Lance in Antioch. It was housed in the Church of the Holy Sepulchre under the protection of the Latin Patriarch, who marched with it ahead of the army before every battle. It was captured by Saladin during the Battle of Hattin in 1187 and subsequently disappeared.
十字军手头的真十字架实际上是真十字架的一小段，不过按记载是每次十字军行军打仗时都有神职人员特意举着十字架鼓舞，很有可能是十字军将真十字架的残余部分拼在大十字架上。
