BRUSSELS — There are already more than 100,000 international troops in Afghanistan working with 200,000 Afghan security forces and police. It adds up to a 12-1 numerical advantage over Taliban rebels, but it hasn’t led to anything close to victory.

Now, the top U.S. and NATO commander in Afghanistan is asking for tens of thousands more troops to stem the escalating insurgency, raising the question of how many more troops it would take to succeed.

The commander, Gen. Stanley McChrystal, says the extra forces are needed to implement a new strategy that focuses on protecting civilians and depriving the militants of popular support in a country where tribal militias may be Taliban today and farmers tomorrow.

The White House said Tuesday that President Barack Obama has nearly finished gathering information and advice on how to proceed in Afghanistan, where bombings killed eight more American troops. With October now the deadliest month for U.S. forces in the war, many experts question the need for more troops.

“The U.S. and its allies already have ample numbers and firepower to annihilate the Taliban, if only the Taliban would cooperate by standing still and allowing us to bomb them to smithereens,” said Andrew Bacevich, a professor of international relations and history at Boston University, and one-time platoon leader in Vietnam.

“But the insurgents are conducting the war in ways that do not play to (allied) strengths.”

The Taliban rebels are estimated to number no more than 25,000. Ljubomir Stojadinovic, a military analyst and guerrilla warfare expert from Serbia, said that although McChrystal’s reinforcements would lift the ratio to 20-1 or more, they would prove counterproductive.

“It’s impossible to regain the initiative by introducing more foreign forces, which will only breed more resentment and more recruits for the enemy,” he said. “The Soviets tried the exact same thing in Afghanistan in the 1980s with disastrous results.”

McChrystal’s defenders say the U.S. has learned from Soviets’ mistakes. At his instruction, NATO troops are increasingly abandoning heavy-handed tactics.

The U.S. says it’s already adjusting its strategy to shift the focus from hunting down and killing Taliban fighters to protecting civilians — in some cases allowing insurgent units to remain untouched if they are not deemed an imminent threat.

McChrystal has also insisted that ground commanders use airpower only as a last resort and when they are absolutely sure civilians are not at risk. As a career Special Forces officer, McChrystal is likely to use small maneuverable units rather than large, heavily armed formations.

Also, experts say guerrilla numbers are not the most important factor in a counterinsurgency campaign. Instead, the number of U.S. troops depends on more complex calculations, including the size and location of the population, and the extent of the training effort for the Afghan security forces.

Appathurai said the goals of the Afghanistan strategy are key to determining how many forces are required. The goal is to have enough troops in populated areas to protect the citizenry and to provide the forces needed to train the Afghans.

In addition, while there may be as many as 25,000 Taliban, it is not a monolithic group like an army, with a clear chain of command that has to be confronted soldier for soldier. Instead, it is a scattered and diverse mix of insurgents, some more ideologically motivated than others.

There are currently about 104,000 international troops in Afghanistan, including about 68,000 Americans. Afghan security forces consist of 94,000 troops supported by a similar number of police, bringing the total Allied force to close to 300,000 members.