It was a hoax call, but the President of Pakistan didn't know then. The caller, who had been put through as the Indian foreign minister Pranab Mukherjee, was threatening war among India's options in retaliation to the 2008 Mumbai attacks.
Asif Ali Zardari apparently panicked. He called the US embassy in Islamabad, whose officials called Washington to relay the president's concerns, according to leaked US embassy cables made public on Friday.
An alarmed US secretary (presumably, then secretary of state Condoleezza Rice) called Mukherjee to "urge calm and during that conversation Mukherjee had backed off from threats," said a cable sent on November 29, 2008.
Though the caller had used an India number, it was not Mukherjee. This was conveyed to by the Indian external affairs ministry to the Pakistani foreign office later.
Although the call had indeed panicked Zardari, but not enough, it seems, for him to talk to his army chief or his foreign minister, both of whom were informed of the call over the next few days by US officials. Not by their president.
"It was clear that Kayani only knew about the November 29 telephone discussions between Zardari and the Secretary and Zardari and FM Mukherjee from Admiral Mike Mullen who had called Kayani earlier in the day," the cable said.
This cable was filed by US embassy after a meeting its officials had with Kayani and ISI chief Shuja Pasha to persuade them to send the ISI boss to India to show seriousness in cooperating with investigations.
Though curious about the so-called call, Kayani had noted, according to the cable, "the Indians appear to have put their air force on alert and armed some of their missiles". He had made it clear though that Pakistan was not reciprocating.
Foreign minister Shah Mehmood Qureshi also learnt about the call from the US embassy. He was surprised as he had heard nothing of this from Mukherjee, who had called him earlier. Qureshi was in India on a visit at the time of the attack.