Lord Louis Mountbatten was assassinated in 1979.

The Irish Republican Army assassinated Lord Mountbatten, a military strategist and mentor to Prince Charles, by planting and remotely detonating a bomb in his fishing boat. The blast killed three others, as well.

The assassination was meant to show that even the pinnacle of British society was not safe from the IRA, as the army attempted to end British rule of Northern Ireland.

According to History.com, the attack, along with another that day that killed 18 soldiers, led to Margaret Thatcher's government taking a "hard-line" stance against the group.