Ordained ministry

Main was ordained a minister of the Church of Scotland on 28 April 1904.^[2][5] He then served as Minister of St Madoes Church, Glencarse, in the Presbytery of Perth until 1912.^[5] He was called to a different church in April 1912, and served as Minister of Old Kilpatrick Church, Dunbartonshire, until 1915.^[6][7] On 20 October 1938, he was nominated as the next Moderator of the General Assembly of the Church of Scotland.^[8] He officially took up the position of Moderator on 23 May, at that start of 1939 General Assembly.^[9]

Main was elected Minister of Kirkbean Church in the Presbytery of Dumfries in 1942.^[10] He retired from full-time ministry on 13 February 1946 due to ill health.^[4][11]

In May 1925, Main was appointed by King George V as a Chaplain-in-Ordinary to His Majesty in Scotland.^[12] He was re-appointed to that position by King Edward VIII (in 1936),^[13] and by King George VI (in 1937).^[14]

Academic career

Main acted as an examiner at the University of St Andrews in political economy between 1906 and 1908, and political economy and modern history between 1912 and 1914.^[3] On 1 October 1915, he was appointed Professor of Ecclesiastical History at the University of St Andrews. He succeeded John Herkless who had been appointed principal of the university.^[7] On 1 October 1922, he was appointed Regius Professor of Ecclesiastical History at the University of Glasgow.^[15] He was the Baird Lecturer from 1935 to 1936.^[4] He stepped down from that Regius Chair in September 1942.^[2][4]

Military service

During World War I, Main served as a military chaplain. On 9 July 1917, he was appointed a temporary chaplain and attached to the 2nd Battalion, Fifeshire Volunteer Regiment, Territorial Force.^[16] He later transferred to the 7th Volunteer Battalion of the Royal Highlanders, Volunteer Force.^[17] On 8 July 1918, he was made a temporary Chaplain to the Forces 4th Class (equivalent in rank to captain) in the Army Chaplains' Department.^[18] He then served in the 9th Volunteer Battalion Royal Highlanders until the end of the war.^[19]

In July 1919, Main was made an Honorary Chaplain in recognition of his war service.^[19] On 31 March 1922, he was appointed a Chaplain to the Forces 4th Class in the Royal Army Chaplains' Department, Territorial Army Reserve.^[20] While a professor at the University of Glasgow, he served as chaplain to the Glasgow University Officers' Training Corps; he stood down in 1942 when he left academia.^[21]