Henry VIII of England wished to unite the Kingdom of Scotland with the Kingdom of England, or at least bring the kingdom under his hegemony. He had contracted with the Regent Arran that Mary, Queen of Scots would marry his son, Prince Edward. But Arran allowed the Parliament of Scotland to revoke this agreement prompting Henry to declare war in December 1543, and now the Regent was making ground against his rebels who still supported the English marriage, such as the Earl of Lennox, Earl of Glencairn, the Earl of Cassillis and the Earl of Angus. These nobles were in touch with Henry VIII via Lennox's secretary Thomas Bishop and Angus's chaplain, Master John Penven. Their letters to Henry VIII requested intervention, and in March he replied that a 'main army' was in preparation. Henry's Privy Council issued his instructions for the invasion force on 10 April 1544, and they were to;
"Put all to fire and sword, burn Edinburgh, so razed and defaced when you have sacked and gotten what ye can of it, as there may remain forever a perpetual memory of the vengeance of God lightened upon (them) for their falsehood and disloyalty."
Edward Seymour, 1st Duke of Somerset, at this time called Lord Hertford was the King's Lieutenant of this Army Royal. He had considered establishing an English garrison at Leith but the Privy Council vetoed this plan. Henry VIII had also asked him to destroy St Andrews, but Lord Hertford pointed out the extra distance would be troublesome.
Hertford discussed with Privy Council the possibility of Scottish allies capturing Cardinal Beaton during his invasion. Henry VIII believed that Beaton, a favourer of the Auld Alliance with France, was particularly responsible for the rejection of the marriage plan. Beaton's would-be kidnappers included James Kirkcaldy of Grange, Norman Leslie Master of Rothes, and John Charteris who offered to attempt to capture the Cardinal as he travelled in Fife. Their second scheme was to attack Arbroath while attention was focussed on Edinburgh. This offer was made by Alexander Crichton of Brunstane who sent a messenger called Wishart to Lord Hertford. Time was too short to offer military support for these plans, but if those concerned would join in the destruction of Church property they would be offered asylum in England and £1000 to fund their action. Any schemes more elaborate than a punitive raid on Edinburgh were shelved as Henry VIII committed resources to the siege of Boulogne in France already planned for the summer.
The army assembled at Newcastle upon Tyne and Gateshead. In April 1544, Sir Christopher Morris reported to Lord Hertford that he had organised munitions for the invasion at Berwick upon Tweed. These included;