President Obama plans to begin withdrawing U.S. combat forces from Afghanistan in the summer of 2011 and to turn over major responsibility for counterinsurgency operations to Afghan forces.

Gen. David Petraeus, the newly appointed combat commander, as well as the U.S. defense chain of command, fully supports this plan though virtually all officials note that the timetable is not an exit but rather initiation of process for engaging Afghan forces more extensively in counter insurgency operations.

This plan envisages U.S. involvement in assisting Afghanistan for many years, so we would not be abandoning the operation, nor should we do so given the vital importance of assuring that terrorists do not gain another foothold for training potential attackers of the U.S., and to destabilize neighboring Pakistan with its large arsenal of nuclear weapons.

In my view this withdrawal timetable is sensible for at least two reasons.

• First, the timetable forces the Afghan government to accelerate efforts, which remain woefully lacking, for improving governance, curtailing endemic corruption and fielding Afghan army forces and national police forces.

Without a date, less Afghan incentive exists to achieve results. We have experienced this unfortunate reality in Vietnam, in Iraq and during the past 10 years in Afghanistan. Moreover, the Russians discovered this reality too late during their 10-year debacle in Afghanistan.

• Second, the timetable forces U.S. military and coalition troops to accelerate Afghan training and counterinsurgency efforts.

Again, without a date the mañana tendency will persist to our mutual disadvantage despite ongoing herculean efforts by U.S. as well as coalition forces to recruit and train Afghan army troops and police.

Some critics of the timetable argue that it gives comfort to the enemy, who will wait us out and reappear in force after we leave.

While some truth exists in this criticism, clearly the U.S. will retain considerable leverage over events in Afghanistan for many years to come. The leverage will exist in the long-term presence of military and civilian advisers, and economic as well as military assistance to the Afghan government and its security forces.

A historical example of leverage may be instructive. During the last year of U.S. withdrawal from Vietnam, when the Viet Cong and North Vietnamese clearly knew that the U.S. was leaving, negotiations on prisoner release broke down. As senior negotiator in Saigon, I faced Viet Cong and North Vietnamese military negotiators who brusquely refused to agree to terms for release of all prisoners.

But fortunately, we still retained some leverage because at the same time we had begun, at North Vietnamese request, the clearance of anti-ship mines in the Haiphong harbor near Hanoi.

When the communist negotiators walked out of the meeting, I directed that all mine clearance operations cease. Within hours, the communist negotiators reappeared to tell me that they would agree to all the conditions for total prisoner release if we would resume clearance of the mines.

Although the example is not entirely analogous to what might occur in Afghanistan with the U.S. withdrawal timetable, it does illustrate that we can still influence future events in positive ways.

In conclusion, the Obama administration's plan to start withdrawal of U.S. combat troops in summer of 2011 and turn over major counterinsurgency operations to Afghan forces makes sense in terms of our own national security interests and for practical and Afghan cultural reasons.

The timetable for withdrawal is not an exit but the beginning of a process.

The timetable might have to be adjusted based on conditions in Afghanistan, but we should support the proven principle of a timetable and Afghan security policy related to it.

Moreover, we must assure that we retain leverage over future developments.

E-mail Gen. John Wickham, retired Army chief of staff, 1983-87, at