The British Flag today has diagonal red stripes through the diagonal white cross -- this is known as the St. Patrick's Saltire.

During the Revolutionary War, the Kingdom of Great Britain flew a flag not unlike the one flown in Great Britain today, but with some noticeable differences. The flag flown during the war lacked the red diagonal stripes -- the Saint Patrick's Saltire -- that appear on the Union Flag today.

The King's Colours Flag

The flag Great Britain used during the Revolutionary War lacked the diagonal red stripes because the Act of Union in 1707 unified England and Scotland -- it excluded Ireland. This flag was called the King's Colours Flag. The St. Patrick's Saltire was added later for Ireland when the new Act of Union was passed in 1800.