Battle Cry

While no meaning has been stated, based on the lyrics it's clear it's about the Jacobite rising of 1745 and the Battle of Culloden. To put a long story as short as possible, the Jacobite rising was a succession in the line through which Jacobites believed that the crowns of England, Scotland, and Ireland should have descended. The Jacobite rising of 1745 was an attempt by Charles Edward Stuart to regain the British throne for his father, James Francis Edward Stuart. The Battle of Culloden was the final confrontation of the Jacobite rising as on April 16, 1746, the Jacobite army of Charles Edward Stuart was decisively defeated by a British government force under Prince William Augustus.

In a bit more detail: The name Jacobitism was a political movement that supported the restoration of the senior line of the House of Stuart to the British throne and the name derives from the first name of James II of England. When James went into exile after the November 1688 Glorious Revolution, the Parliament of England decided that he had abandoned the English throne, and was declared he had "forfeited" the throne by the Scottish Convention. Jacobites argued that monarchs were appointed by God and could not be removed. While this was the most consistent point of contention, Jacobitism was a complex mix of ideas, many opposed by the Stuarts themselves. In Ireland, James supported tolerance for Catholicism but opposed other demands such as Irish autonomy and reversing the 17th-century land settlements. In 1745, clashes between Prince Charles and Scottish Jacobites over the 1707 Union and divine right were central to the internal conflicts that ended Jacobitism as a viable movement.