The apostle Paul's primary concern was to go and proclaim the Gospel to people who had never heard of it.
Likewise today, missionaries travel to various countries, learning languages, and giving their lives to break thousands of years of satanic darkness over peoples who do not know Jesus Christ. They reach out to those who have little or no access to the Good News and minister among them.
And since Jesus' injunction to make disciples of the nations is still relevant today, every church should pray that God will not only make us evangelists in our own lands, but that he will raise up missionaries to take the gospel to hostile territory.
This new book by John Piper on missions inspires a missionary desire to reach people far removed from biblical faith.