When did the 10 tribes of Israel fall apart into just one, the tribe of Judah?
The twelve tribes of Israel were united up until the end of Solomon’s reign.
When Solomon’s son Rehoboam came to the throne he alienated ten of the tribes who seceded under Jeroboam. 1Kings 12:1-17
The tribes of Judah and Benjamin were joined together as the kingdom of Judah in the south with Jerusalem as their capital.
The ten tribes became the kingdom of Israel in the north. Samaria became their capital.
Jeroboam replaced the worship of God at Jerusalem with golden calves set up in Bethel (south) and Dan (north).
The kings who succeeded Rehoboam over the kingdom of Judah were a mixture of good and bad, whereas the those who succeeded Jeroboam over the kingdom of Israel were all bad kings.
As a consequence God allowed the Assyrians to take the ten tribes of Israel into captivity in approximately 740 BC.
The kingdom of Judah was subsequently taken into captivity by the Babylonians in approximately 586 BC.
The captivity of the kingdom of Judah ended when the Persians under Cyrus defeated the Babylonians and allowed the Jews to return to their land.
The kingdom of Judah then continued (without a king) through to the Roman occupation.
In AD 70 the Romans sacked Jerusalem and destroyed the Temple and eventually (approximately AD 132) removed all the Jews from the land of Israel.
This in line with what God had promised if they failed to keep the Covenant he made with them at Sinai.
Joshua 23:16 "When you have transgressed the covenant of the LORD your God, which He commanded you, and have gone and served other gods, and bowed down to them, then the anger of the LORD will burn against you, and you shall perish quickly from the good land which He has given you."
All the tribes of Israel have been outcasts amongst the nations for 2000 years.
But that is not the end. God promised that in the fulness of time they would return to the land and be subjected to a third and final overturning.
Ezekiel 21:27 I will overturn (by the Babylonians), overturn (by the Romans), overturn (by Gog of the land of Magog), it: and it (the kingdom) shall be no more, until he come whose right it is; and I will give it him (Jesus Christ).
Luke 1:31 "And behold, you will conceive in your womb and bring forth a Son, and shall call His name JESUS. 32 "He will be great, and will be called the Son of the Highest; and the Lord God will give Him the throne of His father David. 33 "And He will reign over the house of Jacob forever, and of His kingdom there will be no end."
The final overturning will result in the return of Jesus Christ to save the nation and restore the kingdom of Israel as the kingdom of God on the earth. They will finally recognise him as their Messiah
Israel returned to the land in 1948 and regained Jerusalem in 1967.
Peace has eluded them up to now, but we are awaiting the fulfilling of the prophecies of Ezekiel 38 & 39 and Zechariah 12 to 14.
God promised an eternal inheritance to Abraham and his seed in the land, which guarantees resurrection from the dead to eternal life.
This was made possible by the sacrifice of Christ to make atonement for the sins of the faithful.
Those who believe and obey the gospel preached by Jesus and his apostles become Abraham’s spirititual seed and heirs of the promise of an eternal inheritance in the earth.
Galatians 3:29 And if you are Christ’s, then you are Abraham’s seed, and heirs according to the promise.
I hope this helps,