Jews in Spain opened the Gates of Toledo in 711 to help an invading Muslim army conquer their host country. Spain would become a Muslim country for about 800 years.
In 1492, Christian Europeans took back Spain and one of the first things they did was expel Jews.
One year later, the Spanish Golden Age began.
https://www.judaism-islam.com/jews-opene-the-gates-of-toledo/Edited by Columbian Gold at 11:16:29 on 08/08/24