Just a little context: One of my favorite things to do is play Europa Universalis5 which is a great historical knowledge well I can draw from everyday (even though you can partake in some hilarious historically inaccurate gameplay).

In east Asia, the nations of Aceh and Brunei are depicted as adherents of Sunni Islam, but I was wondering if this is actually accurate. Indonesia is very far away from mainland Asia and the spread of Islam as I know it focused on mainly westward expansion. How did Islam reach Indonesia historically?