Amid the slaughter of Karbala and Baghdad last week, furious Iraqis knew who to blame: supporters of the fallen regime of Saddam Hussein, and the US military, which failed to protect them.
US officials, meanwhile, were pointing to Abu Musab al-Zarqawi, a little-known Jordanian whom Washington believes is linked to Osama bin Laden's al-Qaeda network and who, the Americans allege, has played a key role in months of bloody attacks in Iraq.
For the Bush regime, the Ashura bombings were a blunt reminder of the failure to capture bin Laden and key lieutenants 30 months after the September 11 attacks.
The world's most sophisticated technology and tens of thousands of US troops have failed to provide reliable intelligence on bin Laden's whereabouts since, it is widely believed, he fled Afghanistan's Tora Bora mountains as war raged in late 2001.
But if you believe a string of anonymous sources and the odd US military spokesman, Washington feels its luck might be turning.
First, the US military said it was 'increasingly confident' bin Laden would be captured this year. Days later, Britain's Sunday Express newspaper - quoting 'a US intelligence source' - reported that bin Laden and about 50 supporters had been boxed in among the Toba Kakar mountainous north of the Pakistani city of Quetta and were being watched by satellite.
Pakistan then sent several thousand extra troops to the tribal area of South Waziristan, just to the north. At least 70,000 soldiers are now combing the mountains for what the government calls 'foreign militants'.