The Puritan faction in Parliament made five attempts to appoint an assembly between June 1642 and May 1643, but each time King Charles refused to sign the bill. A sixth bill was prepared and passed as an ordinance of the House of Commons; and, with the agreement of the House of Lords it became effective without the king's assent in June 1643.
With the abdication of the Episcopalians and the deaths of a few others, Parliament determined that an additional twenty-one ministers should be appointed, these to be known as superadded divines. The average daily attendance was between sixty and eighty members. The Assembly's first meeting was in the Henry VII Lady Chapel of Westminster Abbey on July 1, 1643. It later moved to the Jerusalem Chamber of Westminster. It met 1,163 times between 1643 and 1649, and was never formally dissolved by Parliament. During the Interregnum, it met generally only for judicial matters to examine ministers who presented themselves for ordination or induction into vacant charges. The Westminster Assembly was an advisory arm of the Parliament who selected its members, proposed its topics for discussion and delineated its scope of work. Parliament provided an allowance of four shillings per day for each of the divines to defray their expenses. The first task given to the Assembly was revision of the Thirty-Nine Articles. The first ten weeks of the Assembly were expended in debating the first fifteen of the Articles.
The civil war between the forces of Parliament and the Royalists supporting Charles I was at a stalemate. Irish Catholics who had revolted in 1641 were threatening to join the Royalist side. Desperate for help, Parliament sent a delegation to the Scots seeking aid in their civil matter. Though the English sought to enter into a civil league for defense of civil liberties, the Scots quickly responded that the spirit of the contest in which they had been engaged (the Bishop's Wars) was of a religious character, in defense of religious liberty. Eventually the two sides forged a document intended to serve both causes, The Solemn League and Covenant. In return for sending the Scottish army south to support the Parliament, the Scots obliged the English to reform the Church of England "for the preservation of religion in Scotland, the reformation of religion in England and Ireland according to the word of God and the example of the best reformed churches" and the extirpation of prelacy and popery. Six Scottish commissioners were appointed to travel to England to sit with the Westminster Assembly. The Parliaments of England and Scotland eventually required that all persons above the age of 18 in both countries swear to the oath of the Solemn League and Covenant.
On October 12, 1643, the Westminster Assembly received a directive from Parliament that the divines should forthwith "confer and treat among themselves of such a discipline and government as may be most agreeable to God's holy word, and most apt to procure and preserve the peace of the church at home, and nearer agreement with the Church of Scotland and other Reformed Churches abroad." The Assembly abandoned work on the Thirty-Nine Articles and proceeded to create an entirely new set of documents. Over the next four years, the Assembly produced and forwarded to Parliament "The Directory for the Publick Worship of God", "The Form of Presbyterial Church Government", a creedal statement, "The Westminster Confession of Faith", a "Larger Catechism" and a "Shorter Catechism". The House of Commons insisted that the Assembly include scriptural proof texts with the Confession and the two catechisms. The divines also examined and approved the use of Rouse's metrical version of the Psalter in general worship.
All of these documents were debated fiercely. The Erastians, Presbyterians and Independents could never agree on church government. The Independents were thoroughly congregational in their view of church officials. They resisted the idea of church courts and held that members of each congregation should have all power and authority. They agreed that each congregation should choose their own minister, but they opposed regulation and correction of those choices by presbyteries. The Erastians believed in civil authority over the ecclesiastical. In their minds the civil magistrate, being Christian, should have jurisdiction instead of church courts. Sin was to be punished by civil courts, and ecclesiastical bodies should be forbidden from withholding sacraments or excommunication.
The completed work of the Westminster Assembly was eventually adopted with revisions in England, but was revoked during the Restoration in 1660. All of the documents were embraced by the Church of Scotland. Further, they formed the cornerstone of the Presbyterian Church and other reformed churches as they established themselves throughout Europe and America.