The Afghans and the Americans don’t agree on much these days, but both sides are pointing their fingers toward the Pakistan-backed Haqqani network as the force behind the coordinated barrage of attacks in Kabul over the weekend.This news pours cold water on hopes for an improved relationship after Pakistan agreed to allow NATO forces to send ground shipments over Pakistani territory to Afghanistan.Ryan Crocker, the US ambassador to Pakistan, warns that the attack highlights the need for the US to stay the course in Afghanistan. A quick withdrawal, he argues, would pretty much ensure that some of the world’s nastiest groups would once again find a warm welcome in Afghanistan to plan global terrorist attacks.He is right, and there is another reason for concern. So far, the radicals have been the big losers in their military campaigns against the US. Al Qaeda in Mesopotamia was crushed by the US with the help of Sunni Arabs in Iraq who soon came to loathe its barbarity, brutality and bizarre religious interpretations.For groups like Al-Qaeda and its gang of assorted siblings and offshoots, anything that can be perceived as a military victory against the US and its allies is oxygen. The prestige of these groups, in steep decline given their miserable military record, will recover. Recruiting will prosper. Donations will flow.It is a vital US interest to hold on in Afghanistan until there is some kind of agreement that stabilizes the country, more or less. Difficult as that is, it is easier than living with the consequences of an ignominious retreat — and those consequences will be felt far more widely than in Afghanistan alone.Ambassador Ryan needs some help in getting this message out. President Obama really does need to speak up about the war, his war, more clearly and more often. As it is, his silence undercuts the brave soldiers and, yes, diplomats out there on the front lines carrying out the decisions the White House has made.At the same time, the likely involvement of Pakistani government elements in backing Haqqani points to the complexity of the problems the US faces on the ground. And Afghan President Karzai, who seems constitutionally unable to refrain from taking little nips at the hand that not only feeds him but protects him from those who would stone him to death as a blasphemer, is not much help.Still, Afghan government forces appear to be gaining capacity. And other governments in the region are increasingly united in their concern that the worst elements in Pakistan’s security structure have plans for postwar Afghanistan that are unacceptable. Russia, India, China and Iran: none of them can tolerate the kind of Afghanistan that the ISI would like to create.The US path out of this tangle is going to be complicated and tiresome and in the nature of things it cannot be risk-free. But President Obama was right during his 2008 presidential campaign to call this a war of necessity and he was right to conclude in his strategic review that it was better to dig in than to run.The time-limited surge may not have been the most brilliant war plan ever devised, and US strategy needs to evolve in light of events, but at the most basic level the White House was right to see that it was more expensive to run away from Afghanistan than to hold on, and that the only way out involved a strengthening of the Afghan state as a prerequisite for an acceptable peace.Presidential leadership now more than ever is needed to get public support for what remains a necessary though not particularly palatable or glorious war. Somebody needs to speak out and speak up.