In that day the remnant of Israel and the survivors of the house of Jacob will no more lean on him who struck them, but will lean on the LORD, the Holy One of Israel, in truth. A remnant will return, the remnant of Jacob, to the mighty God.
Even before Assyria would destroy the Northern Kingdom of Israel and threaten the Southern Kingdom of Judah, God decreed an end to Assyrian hemogeny in the region. He would leave a remnant. There would be a restoration of His people. And indeed, this did happen.
The Northern capital of Samaria did retain a very small population of ethnic Israelites. The Assyrian invasion led to some intermarrying among the Samaritan population so that what survived as a remnant by New Testament times was more cultural than racial. The Samaritans worshiped God. They did so much more differently than the surviving Judeans. They had their own temple and their own copies of the Law. And most racially "pure" Jews despised them, even though this was how God kept His remnant in the land.
Of course, the citizens of Jerusalem had their own brutal captivity in Babylon, but they managed to keep a strong ethnic identity. And when they returned after 70 years in Babylon, they were never again the idolatrous people that they one were. They had other problems, but paganism was not one of them. They had learned not to lean on the nations around them, but to trust in God.
And then, in Jesus, both groups were joined as one in a unique way. Jesus went out of His way to spend time in Samaria when His contemporary religious leaders avoided doing so. He made a point to tell a story in which a Samaritan embodied the essence of the Law and the true love for God and His neighbor. After His ascension, He saw to it that one of the early advances of the church under the apostles in the Book of Acts was the evangelization of Samaria. He commanded them to preach the gospel there. The Messiah brought all the remnant back into one group and once again God is a Mighty God to His people.
One encouraging truth from these restoration passages is to see the promises of God fulfilled. It strengthens my faith as I see it promised in scripture, played out in history, and delivered in the person of Jesus.