614
The year the Persian Empire (under general Shahrbaraz

) captured and sacked Jerusalem
They damaged the 'Church of the Holy Sepulchre' :< and captured the true cross
In the same year, the Persians destroyed the Ghassanid kingdom .o/
ps: The people from Ghassanid were a large group of emigrated arab christians that lived in fronteir states under the Byzantine Empire.
The people they stem from had to leave their area somewhere around Yemen because their dam broke down and the area flooded, they were scattered all over the then known world, but a large group ultimately found eachother in Ghassanid.
Also, it's not really a kingdom because the kings were called phylarchs.
edit:
Kisa: The Ghassanids originally succesfully opposed some Persian allies... but that didn't really matter because the Persians raided pretty much everything

The Ghassanid people were either killed, got lost, or turned into muslims throughout history

though their last king ruled until 638.