During a mission aboard a rescue helicopter, U.S. Air Force pararescue men, or PJs, give emergency medical treatment to two Afghan Army soldiers wounded in a rocket-propelled grenade attack Monday, over the Arghandab district of Kandahar province, southern Afghanistan. Air Force pararescue men and helicopter aircrews work together to evacuate wounded combatants and civilians from battlefields in southern Afghanistan.

Kabul, Afghanistan ? With U.S. troop strength approaching 100,000, the Afghan war is entering its decisive phase. Without measurable progress in the coming months, political support for the conflict may collapse.

Back-to-back months of record U.S. military death tolls — 60 in June and 66 in July — shocked many Americans, even though the Pentagon had been warning of higher casualties this summer as the U.S. and its allies push into longtime Taliban strongholds around Kandahar city and in the southern province of Helmand.

The campaign is aimed at securing Kandahar, a city of about a half million, the major urban area of the ethnic Pashtun south and the former Taliban headquarters. Securing the city is considered pivotal if the NATO-led coalition is to reverse the Taliban momentum in their southern stronghold.

Failure would be a grave — if not fatal — blow to the entire NATO-led mission in Afghanistan.

It could encourage President Hamid Karzai, who was born near Kandahar, to seek a political deal with Taliban leaders on terms that Afghan ethnic minorities, women and the U.S. might find unfavorable. And it could discourage Pakistan from ever cracking down on Afghan Taliban fighters living in border sanctuaries since they may someday wield power in Afghanistan after the U.S. leaves.

Fighting the Taliban

But progress in breaking the Taliban’s grip has been slow and difficult to measure in a war where the opinions of rural Afghan villagers are as important — if not more — than seizing strategic terrain. It’s hard to explain the deaths of young soldiers without compelling evidence that their sacrifice was worth it.

Supporters of the counterinsurgency strategy which President Barack Obama embraced last year acknowledge that it will take time to determine whether the operations around Kandahar have achieved even modest success.

Even if Taliban attacks decline, it will take time to tell whether the insurgents have been driven off or simply went underground as they did in the Helmand town of Marjah, only to return later with more ambushes and roadside bombs.

Afghan civilians are unlikely to shift their support to the coalition and the Afghan government without compelling evidence that the Taliban are gone and that their own leaders are making good on promises of better public services and good governance.

“We’re at one of those moments where it’s very hard to tell whether things are going well or badly,” Stephen Biddle of the Council on Foreign Relations said in an interview with CFR.org website. “Counterinsurgency always has this ‘darkest before the dawn’ quality.”

Time is one resource that the U.S. and its allies don’t have.

Support for the war is already wavering in Washington and the capitals of the other allied nations that provide troops here. The Dutch ended their combat mission last weekend, and the Canadians plan to pull out next year. The Poles want to leave in 2012.

Last week, Democratic leaders in the House of Representatives had to rely on Republican support to pass the almost $59 billion measure to finance Obama’s additional 30,000 troops in Afghanistan and other programs. Twelve Republicans and 102 Democrats opposed it.

A prominent Republican on the Armed Services Committee, Sen. Lindsey Graham of South Carolina, said congressional support could collapse next year if conservative Republicans withdraw their backing to make Obama look bad and if anti-war Democrats insist on a pullout.

“If, by December, we’re not showing some progress, we’re in trouble,” Graham told CNN’s “State of the Union” on Sunday. “And the question is, what is progress? Without some benchmarks and measurements, it’s going to be hard to sell to the American people a continued involvement in Afghanistan.”

Administration’s goals

With low public support and wavering resolve, the Obama administration has launched a fresh effort to portray U.S. goals in Afghanistan as modest — reminding Americans that Afghanistan was where the Sept. 11, 2001, terrorist attacks were orchestrated.

“We face huge challenges in Afghanistan,” Obama said Monday in Atlanta, where he announced that the U.S. would meet its goal of ending its combat mission in Iraq by the end of this month. “But it’s important that the American people know that we are making progress and we’re focused on goals that are clear and achievable.”

American officials had hoped to ramp up operations in the Kandahar area last spring. But the timetable slipped for numerous reasons, including public opposition within the city to stepped-up military operations and delays in getting enough trained Afghan troops in place.

In recent weeks, however, U.S. and Afghan troops have begun to challenge the Taliban in the lush Arghandab Valley and other districts around Kandahar. American troops are accelerating the training of Afghan police to provide security within the city itself.