The cross was rarely used in early Christian iconography, as it depicts a purposely painful and gruesome method of public execution. The Ichthys, or fish symbol, was used by early Christians. Constantine adopted the Chi-Rho monogram as his banner (labarum). The use of a cross as the most prevalent symbol of Christianity probably gained momentum after Saint Helena, mother of Constantine the Great, traveled to the Holy Land, c. 326 – 328, and recovered the True Cross. The True Cross is the name for physical remnants which, by a Christian tradition, are believed to be from the cross upon which Jesus was crucified.
Theodoret (died c. 457) in his Ecclesiastical History Chapter xvii gives what had become the standard version of the finding of the True Cross:
The True Cross was captured by Saladin during the Battle of Hattin in 1187, and while some Christian rulers, like Richard the Lionheart, Byzantine emperor Isaac II Angelos and Tamar, Queen of Georgia, sought to ransom it from Saladin, the cross was not returned and subsequently disappeared from historical records.All is not lost, however; at various times, especially from a piece of the cross captured by the crusaders in the sack of Constantinople, fragments of the True Cross were distributed as relics. By the end of the Middle Ages so many churches claimed to possess a piece of the True Cross, that John Calvin is famously said to have remarked that there was enough wood in them to fill a ship.
"When the empress beheld the place where the Saviour suffered, she immediately ordered the idolatrous temple, which had been there erected, to be destroyed, and the very earth on which it stood to be removed. When the tomb, which had been so long concealed, was discovered, three crosses were seen buried near the Lord 's sepulchre. All held it as certain that one of these crosses was that of our Lord Jesus Christ, and that the other two were those of the thieves who were crucified with Him. Yet they could not discern to which of the three the Body of the Lord had been brought nigh, and which had received the outpouring of His precious Blood. But the wise and holy Macarius, the president of the city, resolved this question in the following manner. He caused a lady of rank, who had been long suffering from disease, to be touched by each of the crosses, with earnest prayer, and thus discerned the virtue residing in that of the Saviour. For the instant this cross was brought near the lady, it expelled the sore disease, and made her whole."