"The Falkirian War of Independence, much like our surprise when we discover the alien empire bent on our total extermination, was a hell of a wake-up call to the admiralty. It proved why we shouldn't let a planet diversify too much, and how we should always take someone's knowledge of their home seriously. And how did we pay for that mistake? Trillions of credits in assets destroyed? Hundreds of thousands lives lost? Or perhaps the discovery that the UNSC is hard pressed to retake their own colonies if they banded together, in both military and economic spheres?"
―Codename: ANUBIS, in his report regarding the significance of the conflict
The Falkirian War for Independence, more accurately referred to as the Siege of the Gaelic Colonies, was one of the longest and bloodiest conflicts in the Insurrection. Officially marked just before the Falkirian Armed Forces forced the UNSC garrison offworld, the decade-long war would become the rebel's single-greatest attempt at holding off the invading UNSC forces. Compared to most other rebellions, the war was unique in that it was also a conventional war fought by the colonial governments of Falkirk, Sgòthein and Ffyniannus, with each of their armed forces engaging their UNSC equivalents on land, air and space. Their ability to forcibly take control of civilian infrastructure and set up potent fortifications presented a major threat to the UNSC, enough so that they were eventually forced to treat the conflict as an invasion.