Complex sentence: When the Kingdom of Sarawak annexed Brunei's Pandaruan district in 1890, the British did not take any action to stop it, as they did not regard either Brunei or the Kingdom of Sarawak as' foreign' (per the Treaty of Protection).
Split into simpler sentences: When the Kingdom of Sarawak annexed Brunei's Pandaruan district in 1890, the British did not take any action to stop it. They did not regard either Brunei or the Kingdom of Sarawak as' foreign' (per the Treaty of Protection).