The militancy has spread far beyond the country’s borders, and the mission that President Barack Obama called a "just war" is reaching its finale without its most important aims fulfilled, as many as 50,000 desertions are haemorrhaging Afghanistan's security forces every year.
The latest high-profile defector was a special forces commander who joined the Hizb-e-Islami organisation, a Taliban-affiliated group, taking with him guns and high-tech military equipment.
"He sent some of his comrades on leave and paid others to go out sightseeing, and then escaped with up to 30 guns, night-vision goggles, binoculars and a Humvee," Shuja ul-Mulkh Jalala, the governor of Kunar, said
The US-trained Khan was an officer in a special force unit assigned to conduct complex operations against fighters battling US-led NATO forces and the Kabul government.
Violence has risen in Afghanistan this year as most foreign combat troops prepare to leave by the end of 2014.
Improvised explosive devices, like the latest bomb that struck the wedding party, are the single biggest killer in the Afghan conflict
Nearly two years after the U.S. troop withdrawal, Iraq is in the midst of a deepening security crisis as an al-Qaeda affiliate wages a relentless campaign of attacks, sending the death toll soaring to its highest level since 2008.