There is power in united prayer. Christians are praying for world evangelization in greater numbers and unity than ever before. Already on the annual Global Day of Prayer, hundreds of miillions unite in prayer throughout the world. The motto of Operation World is, "When man works, man works, but when man prays, God works."
We can strategize, harmonize, dialogue and worship - we can equip ourselves with the best financial resources and the most astute missiology available - but without prayer, we will not see spiritual strongholds broken down, nor the unevangelized peoples experiencing the gospel. The state of the gospel changes by prayer.
Source: Jason Mandryk - "The State of the Gospel" in Perspectives on the World Christian Movement: A Reader (4th Edition), Chapter 55, p. 368