Isaiah 52.7-8:
(7) How beautiful upon the mountains are the feet of him who brings good news, who publishes peace, who brings good news of happiness, who publishes salvation, who says to Zion, “Your God reigns.” (8) The voice of your watchmen–they lift up their voice, together they sing for joy; for eye to eye they see the return of the Lord to Zion. (ESV)
Understanding these two verses in their original historical context takes us first to Babylonia, where many of the people of Israel had been deported. They, and eventually their children will live there for 70 years, as prophesied by Jeremiah in chapter 25. During this time the prophets Daniel and Ezekiel lived in exile in Babylonia, and the prophet Jeremiah went and lived in Mizpah of Benjamin in Judea.
But the Babylonian Empire will be defeated by the Medes and eventually ruled by the Persians, and in the year 538 Cyrus will issue the decree for the rebuilding of the Temple in Jerusalem and the return of the exiles of Israel to Jerusalem.
God gave assurance to these exiles as recorded in Jeremiah 29.10: “For thus says the Lord: When seventy years are completed for Babylon, I will visit you, and I will fulfill to you my promise and bring you back to this place”(ESV). And God spoke to the exiles in Ezekiel 34.11-12: “For thus says the Lord God: Behold, I, I myself will search for my sheep and will seek them out. As a shepherd seeks out his flock when he is among his sheep that have been scattered, so will I seek out my sheep, and I will rescue them from all places where they have been scattered on a day of clouds and thick darkness”(ESV). So God promised to the exiles of Israel that He Himself would go visit them and personally lead them back to Jerusalem, in the manner of a shepherd leading his flock back to safety.
Similarly, we may go through times when we think we are abandoned or missed the correct path, but God has already made His way to us through Jesus Christ, Who is the Good Shepherd, to restore us and make us know the certainty of His reign and sovereignty over our lives.
I believe that the verses of Isaiah 52.7-8 are a picture of a messenger going ahead of the return of the exiled people, advancing through the mountains on his way to deliver his message to Jerusalem. This messenger goes like a forerunner before the Lord, who is personally the leader and shepherd of the return of the exiles of Israel to Zion. The route of this return appears most likely to have been in a northwesterly direction along the Euphrates River, and then turning in a southwesterly direction through the Syrian desert. The path then moved in and through the mountains of Israel, likely moving around the Sea of Galilee to the west and on to Jerusalem. So if the route followed this general course, the messenger would have gone through desert and mountains.
These verses of Isaiah also have further application in the New Testament, relating to evangelists communicating the gospel. I believe the verses of Isaiah 52.7-8 are closely connected to Isaiah 40.3-5, since both refer to a messenger who announces good news in advance of one who is coming. And all these verses point to the eventual appearing of the Messiah to Israel, who is the coming of God in the person of Jesus Christ.