The very zeal of Jehovah of armies will do this.
Those words refer to what the rulership of God’s Son will accomplish. They emphasize our heavenly Father’s active interest in the salvation of mankind. Jehovah’s example of zeal clearly indicates that our God-given work as Kingdom proclaimers deserves our wholehearted support, our enthusiasm, our zeal. Our burning desire to help people get to know God is a reflection of Jehovah’s zeal. As God’s fellow workers, then, are we personally determined to have the fullest share in proclaiming the good news that our circumstances will permit? Consider, too, Jesus’ zeal. He set a perfect example of zealous perseverance in the ministry. Despite bitter opposition, he maintained his zeal for the preaching work right to the painful end of his earthly life. As the time for his sacrificial death drew near, Jesus’ determination to help others come to know Jehovah intensified.
The verse extracted from Isaiah does not apply to the preaching work of Jehovah’s Witnesses. The context has to do with God intervening directly in human affairs through the Kingdom of Christ, with the result that all wars and bloodshed will cease. “For you have shattered to pieces the yoke of their load, the rod on their shoulders, the staff of the taskmaster, as in the day of Midian. Every boot that shakes the earth as it marches and every garment soaked in blood will become fuel for the fire.” – Isaiah 9:4-5
But before the very zeal of Jehovah of armies abolishes war forever, first must come the Demolisher of nations.