Brad Pitt and Angelina Jolie decided to get married because of her work with the United Nations. Apparently the couple feared she may not survive a dangerous new mission with the UN helping to battle drug lords.

The mother of six adopted and biological children, who is a goodwill ambassador for the UNHCR refugee organization, will be involved when the UN launches a fresh war on South American crime bosses. "Brad's terrified something bad will happen to her. It's why he wanted to cement things with a wedding," a source told The Sun.

Earlier this year Angelina wrote a farewell letter to her fiance Brad after becoming scared for her life on a UN mission. "I wrote a note to Brad and figured if anything happens he'll find it. They gave me a briefing and they said everybody needs to write down their blood type," she said.

The couple - who met on the set of Mr. and Mrs. Smith in 2005 - have kids Knox, Vivienne, Pax, Shiloh, Zahara and Maddox together. They announced their plans for a wedding last month.