Complex sentence: He subjugated the people of those areas and took their children as slaves, then he fought against Najran for their help to Hadhramaut and defeated them taking 1,000 of their children as captives and slaves to his Ghumdan Palace.
Split into simpler sentences: He subjugated the people of those areas and took their children as slaves. Afterwards, he fought against Najran for their help to Hadhramaut and defeated them taking 1,000 of their children as captives and slaves to his Ghumdan Palace.