FORWARD OPERATING BASE SHANK, Afghanistan — Veterans of Iraq recall rolling to war along asphalted highways, sweltering in flat scrublands and chatting with city-wise university graduates connected to the wider world.

Now fighting in Afghanistan, United States soldiers invariably encounter illiterate farmers who may never have talked to an American as they slog into remote villages on dirt tracks through bitterly cold, snow-streaked mountains.

"Before deploying here we were given training on language, culture, everything. I thought that since I was an Iraq combat veteran, I didn't need any of that stuff. I was wrong. Both countries may be Muslim but this is a totally different place," says Sgt. Michael McCann, returning from a patrol in the east-central province of Logar.

While their experiences in the two war zones vary, for many soldiers in the field — if not policy makers — the conflict in Afghanistan is one they think may prove harder and longer to win.

Soldiers and officers involved in combat operations all cite the more punishing geography and climate, those focused on development the bare-bones infrastructure, and intelligence specialists the even greater difficulties in identifying the insurgents as among the many sharp contrasts between Afghanistan and Iraq.