Disputes and disorder :

Where the oighreachd, land owned by the clan elite or fine, did not match the common heritage of the duthchas this led to territorial disputes and warfare. The fine resented their clansmen paying rent to other landlords, while acquisitive clans used disputes to expand their territories, and many clan histories record ferocious long lasting feuding such as the Clan Gordon and the Clan Forbes, which lasted for century and caused many deaths in both clans. On the western seaboard clans became involved with the wars of the Irish Gaels against the Tudor English, and a military caste called the buannachan developed, seasonally fighting in Ireland as mercenaries and living off their clans as minor gentry, but this was brought to an end with the Irish Plantations of James VI of Scotland and I of England. During that century law increasingly settled disputes, and the last feud leading to a battle was at Mulroy in Lochaber on August 4 1688.

Reiving had been a rite of passage, the creach where young men took livestock from neighbouring clans. By the 17th century this had declined and most reiving was the spreidh where up to 10 men raided the adjoining Lowlands, the livestock taken usually being recoverable on payment of tascal (information money) and guarantee of no prosecution. Some clans offered the Lowlanders protection against such raids, on terms not dissimilar to blackmail.

Although by the late 17th century disorder declined, reiving persisted with the growth of cateran bands of up to 50 bandits, usually led by a renegade of the gentry, who had thrown off the constraints of the clan system. As well as preying off the clans, caterans acted as mercenaries for Lowland lairds pursuing disputes amongst themselves.

Civil wars and Jacobitism :

As the civil wars of the Three Kingdoms broke out in the early 17th century the Covenanters were supported by the territorially ambitious Argyll Campbells and House of Sutherland as well as some clans of the central Highlands opposed to the Royalist House of Huntly. While some clans remained neutral, others led by Montrose supported the Royalist cause, projecting their feudal obligations to clan chiefs onto the Royal House of Stuart, resisting the demands of the Covenanters for commitment and reacting to the ambitions of the larger clans. In the Wars of 1644-47, the most prominent Royalist clan were Clan Donald led by Alasdair MacColla.

With the Restoration of Charles II Episcopalianism became widespread among clans, which suited the hierarchical clan structure and encouraged obedience to Royal authority, some others were converted by Catholic missions. In 1682 James Duke of York, Charles' brother, instituted the Commission for Pacifying the Highlands which worked in co-operation with the clan chiefs in maintaining order as well as redressing Campbell acquisitiveness, and when he became King James VII he retained popularity with many Highlanders. All these factors contributed to continuing support for the Stuarts when James was deposed by William of Orange in the "Glorious Revolution".

The support among many clans, their remoteness from authority and the ready mobilisation of the clan hosts made the Highlands the starting point for the Jacobite Risings. In Scottish Jacobite ideology the Highlander symbolised patriotic purity as against the corruption of the Union, and as early as 1689 some Lowlanders wore "Highland habit" in the Jacobite army.

Decline of the Clan system :

Successive Scottish governments had portrayed the clans as bandits needing occasional military expeditions to keep them in check and extract taxes. As Highlanders became associated with Jacobitism and rebellion the government made repeated efforts to curb the clans, culminating with brutal repression after the battle of Culloden. This followed in 1746 with the Act of Proscription, further measures making restrictions on their ability to bear arms, traditional dress, culture, and even music. The Heritable Jurisdictions Act removed the feudal authority the Clan Chieftains had once enjoyed.

With the failure of Jacobitism the clan chiefs and gentry increasingly became landlords, losing the traditional obligations of clanship. They were incorporated into the British aristocracy, looking to the clan lands mainly to provide them with a suitable income. From around 1725 clansmen had been emigrating to America; both clan gentry looking to re-establish their lifestyle, or as victims of raids on the Hebrides looking for cheap labour. Increasing demand in Britain for cattle and sheep led to higher rents with surplus clan population leaving in the mass migration later known as the Highland Clearances, finally undermining the traditional clan system.