The Cross of Burgundy (Spanish: Cruz de Borgoña) was used most prominently by Spain as a naval flag until 1701 and land battle flag until 1843. It is inspired on the Cross of Saint Andrew and was used on the standards of King Philip the Handsome as early as 1506, following his marriage to Joanna of Castile. The dukes of Burgundy allegedly used the cross during the Hundred Years’ War (1337 – 1453), hence why it is called Burgundian.
I like very much this cross, but it is ironic that the most famous emblem of the Spanish Empire has a French origin. Burgundy is a French territory at present.
It's not really "French", I believe. The cross refers to St. Andrew (like the flag of Scotland), and was already used by Burgundian dukes during the 100 Years War, when Burgundy supported England against France. It was adopted on the standards of Philip the Handsome (son of Maximilian I of Habsburg) when he married Joanna of Castile (known as "the Mad") in 1506.
Yes, it's true. The Cross of St. Andrew is used in other countries, like Scotland or Russia as naval flag. The "original" cross did not have these "pruned branches", i believe. This version, with the pruned branches, was created in Burgundy, and for this reason this cross is called the Cross of Burgundy to distinguish between this vesión and the original cross. Nowadays, many people believe that this cross represents to the Fascism and to the Carlism, because this flag was used by these movements from the Carlists Wars in 19th century, but it's a great mistake in my opinion.
In some parts of America, this flag still is used in castles.