NAHR-E SARAJ, Afghanistan—In 26 years as an Afghan soldier, Col. Abdul Sboor has fought for the Russians against the mujahedeen and for the mujahedeen against the Taliban. Now he's fighting alongside the local British battle group helping train Afghan soldiers and police to try to take control of their country's security.

For coalition forces, a successful withdrawal from Afghanistan over the next few years rests in the hands of men like Col. Sboor and Lt. Mohammed Wali, the local heads of the Afghan National Army and Afghan...