History shows that the cross was used centuries before Christ. For example, in the British Museum is a statue of the Assyrian king Samsi-Vul, son of Shalmaneser. Around his neck is an almost perfect Maltese cross. On an accompanying figure, that of Ashur-nasir-pal, is a similar cross.
The ancient Greek goddess Diana is pictured with a cross over her head, in much the same way the "Virgin Mary" is represented by many medieval artists. Bacchus, the Greek god of wine, is often pictured wearing a headdress adorned with crosses. Different types of crosses were used in Mexico centuries before the Spaniards arrived. The Egyptians used cross symbols in abundance, as did the Hindus.
The surprising thing is that the "Christian" use of the cross did not begin until the time of Constantine, three centuries after Christ. Archaeologists have not found any Christian use of the symbol before that time. According to one writer (W. E. Vine, Expository Dictionary of New Testament Words, article "Cross"), the cross as a "Christian" symbol was taken directly from the pagans.
The New Testament does not specifically describe the instrument upon which Christ died, though Acts 5:30; 10:39; and 13:28-29 refer to it as a "tree." The Greek word xulon, translated "tree" in these verses, can mean a stick, club, tree, stake, or other wooden articles.
There is absolutely no evidence that God's true church ever used the cross symbol for any purpose. Nowhere does the Bible command its use. It surely would if God expected this of Christians.