How Islam's Doctrine Shifted to Justify Conquest

1. The Mecca period, friendly toward Christianity

In the early 7th century, when Muhammad first began preaching Islam in Mecca, his movement was very weak. So to survive, he strongly emphasized that Muslims and Christians shared the same roots.
That's why the Qur'an praises Jesus ('Isa) as a great prophet sent by God and calls Christians "People of the Book," believers in the same scripture.
At that point, Christians weren't enemies to fight but brothers to live alongside.

2. Once it grew strong, Islam changed its tune

After the Hijra in 622, when Muhammad moved to Medina, everything changed. With an army and political power in Medina, calling Christians brothers became an obstacle.
If the two religions were the same, followers would have no reason to stay with Islam. It's the same principle as religions today teaching that other groups are heretics to keep members from leaving. From then on, Islam began building walls, claiming that Christians had distorted the Bible.

And to lock this interpretation in permanently, the principle of naskh (abrogation) was formalized: later verses in the Qur'an override earlier ones.
Many classical interpreters held that the Meccan-era verse "There is no compulsion in religion" (2:256) was overridden by the Medinan-era "Sword Verse," "Kill the polytheists wherever you find them" (9:5).

3. Doctrine that changed for the sake of spoils

Once the line was drawn that "we are different," there was a very convenient excuse for taking the wealth of Christian lands. If the religions are the same, taking a brother's property is theft. If they're different, it's a holy war to conquer those on the wrong path.
The dhimmi system, under which Christians in conquered lands paid a poll tax (jizya) in exchange for protection, was a clever way of collecting money while showing Islam to be the superior religion. Leaders twisted interpretations of the Qur'an to make the lands and treasures of Christian nations legitimate spoils.

4. Islam even silenced God's own voice

The leaders who fixed the interpretation of conquest through naskh didn't stop there. They established the doctrine of the "Seal of the Prophets," that Muhammad was the final prophet, effectively shutting God's mouth so that no new word could ever come.
In 632, the first caliph, Abu Bakr, used the Ridda Wars to eliminate militarily everyone claiming new revelation.

The Old Testament prophets delivered God's word fearlessly even before kings, and even King David bowed his head before their rebuke.
But Islamic leaders locked God's voice inside a book and nailed it shut so it could never come out again.

The interpretation that justified conquest was fixed forever, and any intervention by God that might correct it was blocked forever.

A Qur'an trapped in civil wars and terror

The result has been power struggles among leaders and endless civil wars, with innocent people bleeding.
Now that there are no more nations left to conquer, those two locks need to be opened from within. It's time to listen again to what the Qur'an itself records about Jesus, and to what God originally did: the voice that rebukes power and cares for the weak.