The O'Donnell clan, like the O'Neill clan, was of the larger tribe known as the Ui Neill, but that didn't stop them from being sworn enemies. In fact, it probably contributed directly to the enmity between these powerful groups, as each could claim to be regional kings with roughly equivalent authority and lineage.

For centuries, the two warred with each other for dominance in the northern parts of Ireland. The O'Donnells sometimes gained a temporary advantage by siding with the English, but this was never more than a cynical short-term strategy to enhance their own local power at the expense of their rivals.

The O'Neills did the same thing from time. The two clans clashed again and again- at Knocakavoe in 1522 (an O'Donnell victory), at Farsetmore in 1567 (another O'Donnell victory). Then the unthinkable happened.

The O'Donnell prince and chief at the start of the 1590s was Red Hugh O'Donnell. Kidnapped by the English, he was held prisoner in Dublin Castle to prevent him from leading his people. The O'Neill chief was Hugh O'Neill, widely considered to be an English lackey. When Hugh O'Neill helped Hugh O'Donnell to escape from Dublin Castle, the two men became allies and friends, and together they staged the last great rebellion of Gaelic Ireland.

Even though the rebellion went down in defeat at the Battle of Kinsale in 1601, the alliance between these former enemies is an inspiring story of what can be accomplished when people put aside their petty differences in service of a higher and more patriotic ideal.