What is a Tau Cross?
The Tau Cross, also called the Cross of Tau, the Franciscan Tau Cross, the Cross of St. Francis, and the Cross of St. Anthony, is a simple cross, based on the Greek Τ, which is pronounce taw. In Hebrew the letter is pronounced the same but written as x. It predates the cross of the crucifixion, and for this reason it is also called the Old Testament cross.
It is a type of the cross of the Crucifixion. In Ezekiel, an angel, traditionally believed to be St. Gabriel, is instructed by God to go and mark the foreheads of the faithful with the Tau symbol. Other angels are then instructed to “go ye after him through the city, and strike: let not your eyes spare, nor be ye moved with pity. Utterly destroy old and young, maidens, children and women: but upon whomsoever you shall see Thau, kill him not, and begin ye at my sanctuary.” (Ezekiel 9:5-6). So in Ezekiel, those marked with the Tau were saved from this destruction – their lives were spared. In the Passion, the crucifix became the symbol of Christ’s sacrifice, which brought eternal salvation. And so yet another name for the Tau Cross is the Anticipatory Cross.

Tradition holds that in the 3rd century, St. Anthony, the Egyptian hermit who is considered the father of monasticism carried a Tau cross, but it was St. Francis and the Franciscan order that really popularized the use of the Tau cross. Francis was also familiar with the religious community that followed in the footsteps of St. Anthony the hermit, a community which was active in Assisi during St. Francis’s time. This is likely where he first encountered the Tau Cross.

In 1215, at the Fourth Lateran Council, Pope Innocent referenced the Tau cross and the passage from Ezekiel. It is widely believed that St. Francis was present at the Council and that this is when he wholeheartedly embraced the Tau cross as his symbol. Francis used it in his writings, painted it on walls and doors where he stayed, and even used it as his signature. St. Francis would also stretch out his arms, to show his friars that their habit was also the Tau Cross. He instructed them to not only let that serve as a reminder, but also as an active symbol for them to be a walking crucifix in their lives.

Due to St. Francis’s love for the Tau Cross, it became associated with the Franciscan Order. It is adopted and used or worn by many followers of St. Francis, whether part of the religious order or secular. Even for those unfamiliar with the details of St. Francis’s life, the Franciscan Order is what comes to mind when most people see the Tau Cross.

More about the Franciscan Orders:

First order

The existence of the Friars Minor or first order dates from 1209, when St. Francis obtained an approval from Innocent III of the simple rule he had composed for the guidance of his first companions. The rule was subsequently rewritten by St. Francis and solemnly confirmed by Honorius III in 1223.

Second order

1212 brought the foundation of the Poor Ladies (also called the Poor Clares) or second order. In that year St. Clare had asked St. Francis to be allowed to embrace the new manner of life he had instituted, with several other pious maidens who had joined her. St. Francis did not write the formal rule for these ladies. It was composed about 1219 by Cardinal Ugolino and later rewritten by Clare with the aid of Cardinal Rinaldo. The revision was approved by Pope Innocent IV in 1253.

Third order

Tradition holds that the foundation of the Brothers and Sisters of Penance, now known as tertiaries, took place in 1221. This third order was established for those men and women who wished to follow Francis’s rule but because of marriage or other ties, could not join the first or second order.
"Lord, grant that I might not so much seek to be loved as to love."
                                Francis of Assisi