The modern missionary movement was a period of intense global gospel proclamation that emerged in the 18th and 19th centuries, fueled by a renewed Calvinistic commitment to the Great Commission and the Doctrines of Grace. It transformed the global landscape by bringing the gospel to "every creature," while emphasizing that the church's mission is to be carried out by those whom the Lord calls and empowers.
The modern missionary movement finds its authority in the Matthew 28:19-20 command to teach all nations. The Lord Jesus, who died and rose again, commissioned His disciples to carry the tidings of salvation to the ends of the earth. As noted in Mark 16:15-20, the disciples went forth with the Lord working with them to confirm the word. The 1689 LBCF teaches in 1689 LBCF Ch.28 §2 that these holy appointments are to be administered by those duly called and qualified according to Christ's commission. This movement was not merely an organized effort of men, but a work of the Holy Spirit, as seen in the early church where the Lord of the harvest raised up messengers to proclaim His gospel among the nations.
The engine of this movement was the effusion of the Holy Spirit, which fits believers for effectual work. As described in Acts 2:1-12, the outpouring of the Spirit at Pentecost was the true power behind the spread of the gospel. According to Plain Theology for Plain People, the spiritual unfruitfulness often seen in churches is frequently linked to a lack of earnest and believing prayer. When believers unite in prayer for the gospel, the fields of the world begin to flourish like the garden of the Lord. The gospel is the A to Z of this mission; it is the announcement of what God has done in Christ, rather than advice about human effort, reminding us that we are accepted in Christ, therefore we obey by seeking the lost.