I know a missionary that serves Iranians. The country is so hostile to Christians that the main, missions strategy is to reach Iranians outside of Iran. Then, they go back in and maybe talk to their own people. Eventually, they get ejected or something worse happens to them, too. There's always a narrow window where people can hear or share the Gospel. Then, discipleship in a high-persecution regime is usually done in secret churches whose meetings are even more difficult.

Under such regimes, the hope is that a sprinkle of people here and there come to know Christ. They immediately have eternal life with forgiveness of sins. Over time, as they share Christ and His Word, more lives will transform as a side effect of the sanctification process. As they do, and people witness it, hearts and minds might change over time in a way that changes the whole country (or its leadership).