Isaiah 19 is titled: "The burden of Egypt" (Isaiah 19:1). The chapter deals with the judgment of Egypt (Isaiah 19:1-15), the salvation of Egypt (Isaiah 19:16-22), and the blessings on Egypt and Assyria (Isaiah 19:23-25). The chapter begins with this announcement: "Behold, the LORD rideth upon a swift cloud, and shall come into Egypt: and the idols of Egypt shall be moved at his presence, and the heart of Egypt shall melt in the midst of it." (Isaiah 19:1). Although this clearly places the general time of the prophecy at the coming of Christ in glory (the Second Coming at the end of the Tribulation), the events of the chapter probably occur at the end of the Tribulation and at the beginning of the thousand year reign of Christ.
The Egyptians will be given "over into the hand of a cruel lord" (Isaiah 19:4). Their river (the Nile) "shall be wasted and dried up" (Isaiah 19:5). Egypt will be "seduced" (Isaiah 19:13) and "shall be afraid and fear because of the shaking of the hand of the LORD of hosts" (Isaiah 19:17). At this point, Egypt will turn to the Lord. They will build Him an altar (v.19) and will "cry unto the LORD because of the oppressors, and he shall send them a saviour, and a great one, and he shall deliver them" (Isaiah 19:20). The "LORD shall be known unto Egypt" (v.21). Because of this chapter's connection with the coming of the Lord (v.1) and because of the blessings that follow (v.23-25), these events must be at the end of the tribulation. As amazing as it may seem to those of us who know the history of Egypt, Egypt will be one of the righteous nations that enters into the kingdom age. Surely, this is great grace!
Perhaps the key verse of the chapter is Isaiah 19:22, which states, "And the LORD shall smite Egypt: he shall smite and heal it: and they shall return even to the LORD, and he shall be intreated of them, and shall heal them." This healing includes multiple blessings. One of those blessings is the joining of Egypt with Israel and Assyria by a great highway and as "a blessing in the midst of the land" (Isaiah 19:23-24). Assyria is roughly modern Iraq--this also is amazing. This must be the time of the kingdom reign of Jesus Christ. The phrase, "in that day," is used six times in the later part of this chapter (Isaiah 19:16, 18, 19, 21, 23, 24). This phrase is often used in connection with the kingdom reign of Christ.
The key to understanding the chapter may be to see the events overlapping the coming of Christ in power and great glory. The chapter cannot be entirely placed in the tribulation or in the kingdom. It must begin in one and end in the other.