Isaiah 2.1-4 [ESV]
The word that Isaiah the son of Amoz saw concerning Judah and Jerusalem. 2 It shall come to pass in the latter days that the mountain of the house of the LORD shall be established as the highest of the mountains, and shall be lifted up above the hills; and all the nations shall flow to it, 3 and many peoples shall come, and say: “Come, let us go up to the mountain of the LORD, to the house of the God of Jacob, that he may teach us his ways and that we may walk in his paths.” For out of Zion shall go the law, and the word of the LORD from Jerusalem. 4 He shall judge between the nations, and shall decide disputes for many peoples; and they shall beat their swords into plowshares, and their spears into pruning hooks; nation shall not lift up sword against nation, neither shall they learn war anymore.
All the nations will flow to God’s mountain where he will teach them how to live. A word like “nations” may seem nebulous until we start thinking of specific examples. Just imagine people from Brazil, China, Russia, and Canada traveling to Jerusalem to learn how God wants them to live.
Furthermore during these “latter days” God will settle the disputes between nations rather than leaving it to the armies of the world to use their weapons to do the job. God will make war so obsolete that even the weapons will find better use as tools for agriculture and the academies training soldiers will simply close down never to reopen.
Note that everything described in this prophecy assumes our earth as the arena of redemption.