Matthew 15:24 “But he answered and said, I am not sent but unto the lost sheep of the house of Israel.”
Rather than “lost”, the Greek says, “put away and punished”. Scripture also defines the word sheep in seven verses as Israel. After the divorce of the Ten Northern Tribes, Jeremiah 3:8, God sent them and most of the Southern Tribes into a temporary captivity with Assyria, Hosea 1, 2 Kings 17-19.
Isaiah 10:5 “O Assyrian, the rod of mine anger, and the staff in their hand is mine indignation.”
When they escaped, their way to the old land of Israel was “hedged up with thorns”, Hosea 2:6. So they went North over the Caucasus mountains and became known as Caucasians. That path through the mountains is also called the “Pass of Israel” even today.
They were “far off” in Europe at the time of Christ, but called Nations, incorrectly Gentiles, by scripture. They are the promised people to be grafted back in to the Commonwealth of Israel under one head, Christ, Romans 11, Ephesians 2 and Hosea 1. No missionaries had to stay a lifetime trying to convince them to become Christians. Once heard, it spread quickly on its own. In fact the Druids had been anticipating its arrival.
Most of true Israel is Christian today. Christ did not fail.