Wars of necessity must meet two tests. They involve, first, vital national interests and, second, a lack of viable alternatives to the use of military force to protect those interests. World War II was a war of necessity, as were the Korean War and the Persian Gulf war.
Then he sketches some alternatives:
One would reduce our troops’ ground-combat operations and emphasize drone attacks on terrorists, the training of Afghan police officers and soldiers, development aid and diplomacy to fracture the Taliban.
A more radical alternative would withdraw all United States military forces from Afghanistan and center on regional and global counterterrorism efforts and homeland security initiatives to protect ourselves from threats that might emanate from Afghanistan. Under this option, our policy toward Afghanistan would resemble the approach toward Somalia and other countries where governments are unable or unwilling to take on terrorists and the United States eschews military intervention.
I don't know how much Haass knows about training security forces, but his first "alternative" would require an investment in Afghanistan as massive as the one we're already making. So I think it's more an operational alternative than a strategic one. But what about the second option? Do you guys think it would protect U.S. and allied interests? Thoughts from the readership?