Opium production in Afghanistan declined 19 percent last year. This was not a random event. Several years of NATO operations in Afghanistan's Helmand province have hurt the drug business. Most of the world's heroin (and much of the opium) comes from Helmand. This province is the center of Taliban power in Afghanistan, and the drug gangs allied with the Taliban to create the ideal place to grow poppies, and turn the opium (derived from poppies) into heroin. But the NATO forces went after the poppy crops and the (smuggled in) supply of chemicals needed to turn the opium into heroin. The improvised labs that did the work were sought out and destroyed. The Taliban and drug gangs fought back, but were outgunned and outfought. All this violence was bad for business.
NATO troops have found that in areas where there were no Taliban, there was much less poppy cultivation. Without Taliban to provide security, there were very few heroin labs or drug markets (where bulk opium or heroin was sold to smugglers). Thus the goal in Helmand is to drive the Taliban out. Sensing this, the Taliban have been trying to expand to other parts of Afghanistan, where there are Pushtun tribes (the Taliban were founded, and largely staffed by Pushtuns from around Kandahar and nearby Helmand). But the Pushtun tribes in the north (where Pushtuns are a minority) were hostile to the drug business. The majority of Afghans (Pushtuns are only 40 percent of the population) have fought against poppy and opium production.
Despite all the corruption, and government officials on the drug gang payroll, the export value of the opium and heroin fell from $3.4 billion in 2008 (a third of GDP) to $2.8 billion (a quarter of GDP) last year. Few Afghans are prospering from the drug trade, and many more are suffering (violence, addiction). Thus the drug trade is restricted to less than 20 percent of the country, and that is where the war is being fought. The Taliban say it's all about religion and tradition. But the guns and gunmen are kept at work because of the cash, and the money comes from the drug trade. That's why NATO is going after the drugs. It's one thing the foreign troops and most Afghans can agree on.