Like all great lovers' tiffs, this one started with frustration. Admiral Mike Mullen, the chairman of the US joint chiefs of staff, decided to make his feelings public.
In a nutshell, he accused Pakistan of state sponsored terrorism, alleging that its Inter-Services Intelligence backs the Haqqani network. The Haqqanis are a fearsome bunch of fighters whose lineage goes back to Soviet occupation of Afghanistan.
Back then, their leader, Jalaludin Haqqani, was seen as a hero, even sitting in the White House with the then President Ronald Reagan. But it wasn't just the US. The Pakistanis nurtured and encouraged him to go fight in Afghanistan, supplying him with weapons and safe havens.
That was 20 years ago and, like all bad marriages, things left unresolved often explode.