A recent Foreign Policy piece by Robert Haddick, managing editor of Small Wars Journal, sketches out this possibility. The article is thought-provoking and at times persuasive — yet also somewhat flawed.

Haddick’s argument is as follows: Kabul regards Taliban sanctuaries in Pakistan as its “number one security problem.” With Pakistan and the United States refusing to smash these safe havens — which the Afghan Taliban and Haqqani network fighters use as staging grounds for attacks on Afghanistan — Kabul will have no choice but to wage its own offensive. This is the only way, Haddick says, for Kabul to gain leverage in efforts to negotiate, with Islamabad and the Taliban, an end to the war in Afghanistan. However, he suggests, sustained Afghan assaults on Afghan Taliban and Haqqani fighters inside Pakistan (widely believed to be proxies of Pakistani intelligence), coupled with Pakistan’s own punitive actions against Afghanistan-based militants and unwillingness to negotiate with Kabul, could spark an “old-fashioned war” between the troubled neighbors.

What Haddick doesn’t say is that Afghanistan’s military is ravaged by desertions, drug abuse, and illiteracy — not to mention militant infiltration. The notion of this fledgling and troubled force barging pell-mell into Pakistan’s tribal belt to crush crafty and vicious fighters who often attack the most well-secured areas of Afghanistan is questionable. Success may be elusive.

Haddick acknowledges Afghanistan’s military would need help, and he proposes an alternative strategy: Kabul reaching out to the Pakistani Taliban — which uses Afghanistan as a base for its insurgency against the Pakistani government — and trying to use the group as leverage over Islamabad.

This reasoning is problematic. It’s doubtful the TTP would want to work with Afghanistan, a country closely allied with Washington — a government the TTP loathes as much as it does Pakistan’s. Additionally, while Haddick doesn’t mention the possibility, it still bears emphasising that the TTP certainly has no desire to fight a proxy war against the Afghan Taliban. True, each has a different chief target (Islamabad for the former, Kabul and Nato forces for the latter). Yet they share much in common, including ethnicity and ideology. And while they are fighting different wars, there is reason to believe they may occasionally cooperate operationally — including, perhaps, in a December 2009 attack on a CIA base in Afghanistan.

Haddick says if Kabul can’t win over the TTP, it would probably ask the United States to “support its development” of offensive capabilities for a military campaign inside Pakistan’s tribal areas. He doesn’t address how Washington would respond to this request, which would present a major conundrum. The recently signed US-Afghan strategic accord states that the two nations will “foster close cooperation concerning defense and security.” However, for a country desperately seeking to extricate itself from an unpopular war, providing support for an offensive inside Pakistan would be tremendously risky. Not only would this antagonise Pakistan, but it would also anger US taxpayers struggling to emerge from economic malaise.

By no means am I saying a war between Pakistan and Afghanistan is out of the question. The possibility certainly exists. Cross-border raids are occurring from both sides of the Durand Line; just last week, dozens of militants from Kunar province raided a village near Bajaur and took villagers hostage. And such incursions are not new. Afghanistan has suffered cross-border assaults for years, and Pakistan is also no stranger to them (recall that last year, 200 militants entered Bajaur from Kunar, and fought Pakistani forces for several days). There are indications that the two governments are starting to lose patience. Afghanistan has claimed that Pakistan’s military fired rockets on suspected TTP camps in Kunar, while Pakistan recently accused 60 Afghan soldiers of pursuing militants in Upper Kurram District.

Still, I think this misses a larger point. With international forces leaving Afghanistan, the country’s internal security situation will surely deteriorate. It won’t be long before Kabul’s “number one security problem” is domestic sources of insurgency, not those across the border. In fact, if, as is likely, Afghanistan descends into chaos once Nato troops depart, many Pakistan-based Afghan militants will likely return to Afghanistan to exploit this unrest — and to attempt to unseat the government.

In essence, not long from now, Afghanistan will be fully consumed with fighting a war within its borders, and not in or against Pakistan.

The takeaway? Washington’s worst-case contingencies about Pakistan are sometimes worth worrying about (economic collapse is a real possibility). But others are not. Sadly, the most realistic nightmare scenarios — such as water scarcity and the disappearance of arable land — are barely acknowledged at all.