After the failure of the Root and Branch Bill, Parliament in 1643 called together the Westminster Assembly of Divines, a body of lay politicians, lords, and clergy whose purpose was to reform church governance. Vane sat on this body, which met periodically until 1648, as one of the lay representatives of the Independent faction. Not long after its first meeting in July, Vane was sent at the head of a Parliamentary commission seeking military assistance from the Scots. The Scots, who had been opposed to Charles in the Bishop's Wars (1639–40) over religious issues, were willing to assist the English Parliament if the latter were willing to allow the extension of the Presbyterian system of church polity to England. Vane was opposed to both Presbyterianism and Episcopalianism, but found a way to finesse an agreement. He proposed that the agreement, which covered a combination of religious and political topics, be called the "Solemn League and Covenant", and he introduced slippery language into the agreement concerning "the example of the best Reformed churches". This language permitted the Scots to believe that their ideas would be adopted, while the English could interpret it to mean that English (i.e. Independent) practices could be adopted. The league and covenant were eventually approved by authorities in Scotland, England, and Ireland, and paved the way for Scottish entry into the war.