In December 2008, the UN General Assembly adopted resolution 63/139, designating 19 August as World Humanitarian Day, chosen to mark the anniversary of the 2003 bombing of UN headquarters in Baghdad, which killed 22 people, including Special Representative Sergio Vieira de Mello. The day was first officially observed on 19 August 2009. The day honors humanitarian workers who risk their lives to deliver aid and protection to millions affected by conflict and natural disasters worldwide, and rallies international support for humanitarian causes. Recent decades have seen a troubling rise in attacks on aid workers and relief facilities in conflict zones, making the day an occasion to highlight the need to protect humanitarian work and uphold international humanitarian law. The day is marked through global awareness campaigns built around a different theme each year, tribute events for humanitarian workers and those who lost their lives in the field, and outreach activities explaining the nature and challenges of humanitarian work to the public.