Writing in July 1650, Robert Blair pressed his friend Robert Baillie, then professor of divinity at Glasgow University, to refrain from defending ministers suspected of supporting the Engagement of 1647. In the previous three years Baillie had come to the support of his colleague and father-in-law, Glasgow principal John Strang, who had been cited for failing to preach against the Engagement and whose orthodoxy and commitment to the National Covenant had come under scrutiny following the discovery in 1646 of his tract defending the rival King's Covenant. At the 1649 General Assembly Baillie had also refused to vote for the deposition of William Colvill, an Edinburgh minister who had failed to oppose the Engagement. For such actions, Baillie, a leading Covenanter, fell under suspicion of ‘malignancy’ and risked expulsion from his post. Blair warned his friend to keep his head down: ‘doe not ye, by intermeddling in that kind, defyle your conscience and destroy your name, which already suffers not a little … Get yow to your book and your work, and meddle not unhappilie to your prejudice.’

Such was the charged atmosphere in Scotland in the wake of the crisis that began in December 1647, when a faction of Scottish nobles signed the ‘Engagement’, a pact promising military assistance to Charles I, who in turn agreed to authorise the Solemn League and Covenant and establish presbyterian Church government for a three-year period in England. Crucially, neither the king nor his subjects would be compelled to take the Covenant against their consciences, which scandalised the Kirk and portions of the Covenanter nobility. The Engagement, however, was not merely an unpopular, and ultimately failed, military alliance. The treaty and its fallout sowed the seeds of schism in the Kirk that would sunder the Covenanting movement entirely. It sparked a crisis in Scotland that threw into question the entire nature of the Covenanting project and brought to the surface competing visions of what precisely defined covenanted Scotland, who should be responsible for facilitating Scotland's formation as a godly, covenanted nation and who could be included in that nation.