Article: John Knox (1505–1572), a Scot who had spent time studying under Calvin in Geneva, returned to Scotland and urged his countrymen to reform the Church in line with Calvinist doctrines. After a period of religious convulsion and political conflict culminating in a victory for the Protestant party at the Siege of Leith the authority of the Church of Rome was abolished in favour of Reformation by the legislation of the Scottish Reformation Parliament in 1560. The Church was eventually organised by Andrew Melville along Presbyterian lines to become the national Church of Scotland. King James VI and I moved the Church of Scotland towards an episcopal form of government, and in 1637, James' successor, Charles I and William Laud, the Archbishop of Canterbury, attempted to force the Church of Scotland to use the Book of Common Prayer. What resulted was an armed insurrection, with many Scots signing the Solemn League and Covenant. The Covenanters would serve as the government of Scotland for nearly a decade, and would also send military support to the Parliamentarians during the English Civil War. Following the restoration of the monarchy in 1660, Charles II, despite the initial support that he received from the Covenanters, reinstated an episcopal form of government on the church.

Now answer this question: What did John Knox do when he returned to Scotland after studying under Calvin?
to reform the Church in line with Calvinist doctrines