Undoubtedly the biggest event of his life was the 'Great Cause' that was concluded in
1292. It gave the Crown of Scotland to his family's great rival,
Balliol, instead of his father. Heiress
Margaret, the Maid of Norway had died in the
Orkney Islands circa
September 26, 1290. With her death, the main line of the
House of Dunkeld came to an end and thirteen
competitors claimed their rights to the Scottish crown. The two main competitors were
Robert de Brus, 5th Lord of Annandale (Robert's father) and
John Balliol, Lord of Galloway. Fearing civil war between the Bruce and Balliol families and their supporters, the
Guardians of Scotland asked the kingdom's southern neighbour,
Edward I of England to arbitrate amongst the claimants.
Arbitration processed slowly. After initial solutions which left two contenders, on
August 3, 1291 Edward asked both de Balliol and de Brus to choose forty arbiters while he himself chose twenty-four, to decide the case. The arbiters finally gave judgement in early November in favour of John Balliol, in accordance with the precedents of primogeniture: even twenty-nine of Bruce's own auditors voted for Balliol, underlining the strength of his claim. On 17 November Edward gave formal judgement in open court; and on
November 30, John Balliol was crowned as King of Scots at
Scone Abbey. On
December 26, at
Newcastle upon Tyne, King John swore homage to Edward I for the kingdom of Scotland. Edward soon made it clear that he regarded the country as his vassal state. The Bruce family thus lost what they regarded as their rightful place on the Scottish throne.
Soon afterwards, his father, Robert de Brus, 5th Lord of Annandale -
the unsuccessful claimant - resigned his lordship to him. And also his claim to crown, in order to prevent it from extinguishing.
Both Robert and his son the new Earl of Carrick sided with Edward I against Balliol. In April
1294, Robert's son had permission to visit
Ireland for a year and a half and, as a further mark of Edward's favour, he received a respite for all the debts owed by him to the English Exchequer. In
1295, his son and heir married his first wife,
Isabella of Mar, the daughter of Donald, 6th Earl of Mar. Isabella died a year later bearing child,
Marjorie Bruce, Robert's granddaughter.
It was not until
1295 that Edward I was even aware of the secret Franco-Scottish negotiations. In early October, Edward began to strengthen his northern defences against a possible invasion by a revitalised Scottish army. It was also at this point that Robert Bruce himself was appointed governor of
Carlisle Castle. Edward also ordered John Balliol to relinquish control of the castles and burghs of
Berwick, Jedburgh and
Roxburgh. In December, more than two hundred of Edward's tenants in Newcastle were summoned to form a militia by March
1296 and in February, a fleet of ships sailed north to rendezvous with his land forces in Newcastle.
The build up of English forces south of the Anglo-Scottish border did not go undetected and in response, King John Balliol summoned all able-bodied Scotsmen to bear arms and converge near the border at
Caddonlee by
March 11.
Balliol seized Robert's Annandale estate and reassigned it to
John 'The Red' Comyn, Lord of Badenoch. Several of the Scottish nobles choose to ignore the summons, including his son
Robert de Brus, Earl of Carrick.
The beginning of the Wars of Independence: In August
1296 Robert and his son swore fealty to Edward I at Berwick, but in breach of this oath, which had been renewed at Carlisle, the younger Robert joined in the Scottish revolt against Edward in the following year.
Shortly after the
Battle of Stirling Bridge, Annandale was wasted as retaliation to younger Bruce's actions. Yet, when Edward returned to England after his victory at the
Battle of Falkirk, Annandale and Carrick were excepted from the lordships and lands which he assigned to his followers, father having not opposed Edward and the son being treated as a waverer whose allegiance might still be retained.
In July, Edward I launched his sixth campaign into Scotland. Though Edward captured
Bothwell and
Turnberry Castle, Edward did little to damage the Scots’ fighting ability and, in January
1302 agreed to a nine-month truce.
Robert at that time was old and ill, and there are reports that he wished his son to seek peace with Edward, who, he was convinced, would be victorious over the Scots. The elder Bruce would have seen that, if the rebellion failed and his son were against Edward, the son would lose everything, titles, lands, and probably his life.
It was around this time that Robert's son submitted to Edward I, along with other nobles, even though he had been on the side of the patriots until now. There are many reasons which may have prompted his turning, not the least of which was that the Bruce family may have found it loathsome to continue sacrificing his followers, family and inheritance for John Balliol. There were rumours that Balliol would return with a French army and regain the Scottish throne. Soulis supported the return of Balliol as did many other nobles, but the return of John as king would lead to the Bruces losing any chance of ever gaining the throne themselves.