What war was behind or about viva la vida?

Answer 1

I don't know the War's name exactly but the song is about the fall of a king.

This war was during the Christian Crusades or the Holy Crusades to gain power of Jerusalem with a clashing religion.

Context clues"I used to rule the world" - simple enough

"Now the old king is dead, long live the king" - resembles the falling of power in his monarchy.

"And I discovered that my castle stands, Upon pillars of salt and pillars of sand" - his monarchy was slowly crumbling beneath him and it was eminent he was going to lose his power.

"Roman Calvalry choirs are singing" - Romans have taken over a city or town and are boasting of their success

"Be my mirror, my sword and shield, my missionaries in a foreign field" - the king is asking for assistant and realizes he is hopeless since all of his missionaries (scouts or people who deliver messages of help) are gone away.

"I know Saint Peter won't call my name" - the reason why this lyric is included because under his ruling, he has been treating others unfairly. and he believes that from his cruelty, he would not be accepted to heaven.