UXO - Unexploded ordnance (bomb) - Laos
Between 1969 ans 1973, the United States drops more than 2,000,000 TONS of bombs on Laos during more than 500,000 bombing missions (more that what it had dropped on Germany and Japan during all of World War II) in an effort to defeat the left-leaning Pathet Lao and to destroy North Vietnamese supply lines. The ordnance includes some 90 million cluster bombs (including the notorious BLU-64B), 20%-30% of which do not detonate. For more information on the secret Laos war, read: en.wikipedia.org/wiki/Laotian_Civil_War.
Unexploded bombs and nasty cluster bomblets still kill and injures thousands of civilians each year in Laos.