It is believed that the apostle Andrew was crucified on a saltire (X-shaped) cross; hence the name St. Andrew's Cross. He is said to have told his executioners that he was not worthy to be crucified on the same cross style as Jesus, and persuaded them to alter the shape. If this is true, it's a remarkable example of stoicism displayed by a man, no doubt beaten and starved, yet retaining the mental energy to plead such a thing with his brutal executioners.
Detailed records of his crucifixion only date back to the Middle Ages, and these records are influenced be the imagination of the medieval artists. But even if the origin is a myth, the cross shape reminds Christians that they should exercise humility.1
In Greek, the first letter for Christ (Chi) also happens to be 'X'-shaped2, as in the Chi Rho Cross.
Instead of simply saying that something is 'X-shaped' or 'saltire', the term 'St. Andrew's Cross' is used for several items that have absolutely nothing to do with St. Andrew or even religion. For example, there's argiope kiyserlingi and the argiope mangal - a tiny, brightly striped spider found in the mangroves of Singapore. These are commonly known as 'St. Andrew's Spiders' because they hold their eight legs in pairs, forming an X shape. Then there's the hypericum hypericoides, a small shrub of the St. John's-wort family. Its flowers form a cross with four yellow petals and is known as 'St. Andrew's Cross'.
The saltire is seen on the American Confederate flag, showing the Scottish lineage of many southerners. On this flag it is known as the Southern Cross.
The saltire is also seen on several national flags, particularly where there is a historical cultural connection with St. Andrew.
For example the white cross on a blue background as the flag of Scotland, and a red cross on a white background as St. Patrick's Cross, representing the patron saint of Ireland. Both of these crosses were superimposed on England's red cross on a white background, St. George's Cross, to give the United Kingdom's Union Flag ('Union Jack')3
The saltire on the flag of Scotland is called 'St. Andrew's Cross'. (This is also the flag of the Saint Andrew and Providence Islands - San Andrés y Providencia - northwest of Colombia, once the settlement of English Puritans, and the flag of Tenerife, Canary Islands, Spain, albeit a slightly darker shade of blue.) The colours are said to come from a white cross made by clouds in the blue sky. In the 9th century, King Angus saw this arrangement on the day before a decisive battle over the English Northumbrian Angles command by Athelstan. King Angus considered it to be a good omen and won the battle. (See also Constantine's Cross.)
Merkill was the place where King Angus' army of Picts and Scots were fighting the King Athel's army of Sassenachs from Northumbria. One night, Angus prayed to God for help in the next day's battle. A vision of Saint Andrew appeared to him, promising victory. The next day, King Angus' men saw two long white clouds streaking across the blue sky forming a cross. They took this as a sign from Saint Andrew and were sufficiently roused to beat the lowlanders in the battle.
Of course, the sign could have been meant for King Athel's men, but perhaps they were too busy fighting to be looking up at the sky. Or were these long clouds the exhaust of jet engines from some early alien visitation? Or 'earthquake clouds'?
Whatever interpretation we wish to make, the Scots believed it was nothing less than a miracle. This battle took place just a stone's throw from a village later known as Markle in East Lothian, Scotland. Markle village has now gone, but a few ruins remain (for example Markle Castle). The original name of the place was Merkill, and this might have come from the word miracle.
The white cross on blue background was adopted as the flag of Scotland and St. Andrew became Scotland's Patron Saint.
It is of no surprise therefore that the St. Andrew's Cross is the basis for many Scottish logos. In particular, the Church of Scotland emblem, which also depicts the miraculous burning bush that was not consumed (Exod. 3).
The burning bush symbol is repeated in the emblems of the Presbyterian Churches around the world and represents the bondage of the church in Egypt.4 Their emblems remind us that the church and its people, in every age and every culture, may suffer severe persecution. And yet God prevents His people from being destroyed.
A similar design seen on the flag of Tallahassee, the capital of Florida, USA, and a variation of the St. Andrew's Cross is the Burgundy Cross. All these crosses represent the Christian religion of the kings at the time the flags were made.
Other national flags have an 'X' cross, but these have no Christian basis.
The flag of Burundi for example, where even though the country is nominally 'Christian', the white cross is not used as a religious symbol. It is a symbol of peace - the goal of everyone after years of ethnic violence between Hutu and Tutsi factions.
The flag of Grenada just happens to have a cross made by the four triangles of wisdom, warmth, vegetation and agriculture. The yellow/gold cross on the Jamaican flag signifies sunshine, as with the Republic of Macedonia's flag. (See also Macedonian Cross)
Now for a children's riddle:
Question: What's black and white and red all over?
Answer: A newspaper!
Without having to use the pun on 'read', we can see that Netherlanders seem to like black, white and red, and they've incorporated those colours into several regional flags with one or more saltires.
There are a few more similar Dutch flags on the Flag Index page, all of which incorporate one or more saltires.
Finally, there's a variation of St. Andrew's cross on the flag of the Vatican (see also Papal Cross). Since the 14th century, two crossed keys have been the official insignia of the Holy See. These keys are the symbols of St. Peter (popes are considered direct descendants of St. Peter's office). The keys were given to Peter (see Matt. 16:19) by Christ to open the doors to paradise, just as the cross opens the gates of heaven for those who believe in Him.
(See other crosses on flags)
But what does the St. Andrew Cross mean for us today? See the meaning of the cross and also read Humility and Sacrifice by Rev. David Linde.