The first large strike between Shia pilgrims and Saudi security forces occurred in 1981. In 1981, this was escalated into openly chanting political slogans in the Masjid al-Haram and the Prophet's Mosque, two of the holiest sites in Islam, resulting in violent clashes with Saudi security and one death. In the same year, King Khalid of Saudi Arabia wrote a letter to Saddam Hussein saying "crush these stupid Iranians" as Saddam pushed on with the invasion of Iranian territory.