It was erected as an apostolic prefecture on 11 March 1935, comprising the civil sub-prefectures of the Sienhsien mission (v.) and entrusted to the Society of Jesus, which for the apostolic work sends thither members of the Hungarian province of the order. On 10 July 1947 it was raised to the status of a diocese, a suffragan of Peking.
It covers an area of 8,640 sq. km. As of 30 June 1947, with a total population of approximately 2,000,000, there were 42,409 Catholics; 34 priests, of whom 9 were Chinese; 30 seminaries, of which 13 were indigenous. Among its works were dispensaries, an orphanage, a hospice for the elderly, and 32 schools with 1,008 pupils.
The evangelization of T., undertaken by the Jesuits of Sienhsien, began in the second half of the last century: in 1857 there were neither Christian communities nor Christians; by 1861 there were 6, rising to 12 in 1864, forming a Christian community. In 1880 there were 23 Christian communities and 399 faithful; by 1910 these had grown to 408 communities and 8,732 faithful, and by 1934— the year preceding the erection of the diocese— to 920 communities and 36,002 faithful.