What factor drove great britain to divide ireland into two states in 1921?

Idk if there is answer choices so idk exactly what youre looking for but as far as I know, Ireland was split because their was a war that occurred because people that lived in Ireland attacked the British rulers.

Ninety years ago Ireland was split in two after people living there went to war against their British rulers.The Partition of Ireland took place on May 3, 1921 under the Government of Ireland Act 1920. The entire island of Ireland provisionally became the Irish Free State on December 6, 1922.

the proximity of water was an advantage to western europe and its culture was able to flourish as a result. trade and travel by sea were easier and safer in historical times.

1. there are no mountains to protect it from the sea

2. and its has wet cool summers and wet, mild winters.