The incredible efforts by our men and women in the field – and increasingly their Afghan counterparts – are pushing the Taliban back but are not causing it to topple. The U.S. military has never lost a battle in Afghanistan, and efforts to clear the Taliban from its strongholds in Kandahar and Helmand have largely worked.

But the Taliban is a shifting and shadowy adversary, and it has adapted in the face of our superior strength. It has ceded ground in the south while increasing its presence in previously peaceful northern Afghanistan, establishing a beachhead with al-Qaeda in the mountainous northeast provinces of Konar and Nuristan, and maintaining its activities with the Haqqani Network in the east.

According to intelligence estimates, the details of which remain classified, the Taliban continues to control or contest territory where more than one-third of Afghans live. These figures have remained stubbornly constant for three years.

The Taliban controls territory not through military force, but through intimidation and coercion of the public and assassinations of government officials. The Taliban believes it can wait out the international security (ISAF) presence.

Taliban leadership, including Mullah Omar, live in Pakistan where they are afforded safe haven. There they are able to direct their insurgent forces, build and resupply improvised explosive devices and provide safe harbor for fighters who are pushed out of their provinces by ISAF and Afghan forces.

The organization has shadow governments in almost every province in Afghanistan, collected an estimated $125 million last year in revenue from taxes on the opium poppy crop and just last month intimidated 14 of 17 districts in Ghazni Province to close their schools.

Even more deadly is the Haqqani Network, which also enjoys safe harbor in Pakistan. According to our commander in Afghanistan, Gen. John Allen, the Haqqanis are responsible for the deaths of more than 500 U.S. troops and conduct most of the high-profile attacks, such as last month’s deadly assault on Kabul.

Problems of corruption at the national, provincial and local level continue to undermine support and trust in the government. A combination of security and history also limit Kabul’s ability to enforce the rule of law and provide services outside of the capital city.

President Hamid Karzai told me that rooting out corruption and implementing civil law were high priorities for him, and I take him at his word. But I also heard that many Afghans support the Taliban simply because it can provide services and deliver swift justice in a way the Afghan government too often cannot.

Clearly, progress has been made. The Afghan National Security Forces and intelligence service are increasing in numbers, capability, literacy and professionalism. The life expectancy of Afghans has increased from 44 to 62 years since the beginning of the war, and perhaps most encouraging, women are an increasingly active part of the government and society; they account for 27 percent of parliamentarians and 40 percent of Afghan students (from nearly zero just a few years ago). Compare this with the total subjugation of women under the Taliban, which also provided Osama bin Laden a base to plan his attacks on the United States.

I heard from President Karzai that Afghanistan will not allow the Taliban to return. Women members of parliament repeated that message, keenly aware that a return to fundamentalist Islam would mean the end of their hard-won rights and personal security.

I hope this is true.

But even if the Taliban does not return to power, it will remain in the shadows, projecting influence around the country and undermining Afghan stability for as long as it has a safe haven across a porous border.

Pakistan must prevent the Taliban, the Haqqanis and al-Qaeda from using its territory. The United States must demonstrate to Islamabad that there are real consequences to providing aid and comfort to those who are attacking and killing American soldiers. The U.S. government should also immediately designate the Haqqani Network as a foreign terrorist organization.

It is also critical that the Afghan people, the Taliban and Pakistan recognize that the United States will have a meaningful and enduring presence in Afghanistan. I recognize that public support for this war, now in its 11th year, has waned. But it is in our own security interests to see a stable and secure Afghanistan, and removing our presence will sacrifice everything that has been gained.

I therefore support the recently signed Strategic Partnership Agreement, which provides for a continued U.S. force presence. The details of our future mission and footprint in Afghanistan have yet to be determined, but the answers will determine whether this war will be ultimately won or lost.

Feinstein, D-Calif., chairs the Senate Select Committee on Intelligence.