Russian President Vladimir Putin, April 11, 2013 REUTERS/Aleksey Nikolskyi/RIA Novosti/Pool

Terrorism always complicates diplomatic relations.

Since the Boston Marathon bombing, the suspected handiwork of two brothers of Chechen background, Russian and American security officials have focused on a blame game.

Could better cooperation between the FBI and the FSB (successor to the KGB) have averted this bombing? Which country is responsible for the carnage? The United States, which Russia warned in 2011 about Tamerlan Tsarnaev, the older brother who was killed in the police shootout a few days after the bombing? Or Moscow, which gave Washington scant evidence to pursue in that query?

During the Cold War, the Soviet Union and the United States regarded each other with a mixture of suspicion and contempt. This continuing legacy may be the reason for the two intelligence services’ failure to communicate here.

The Americans, convinced the other side was withholding information, appear to have mistrusted the inexact Russian data. So the FBI may have decided to do the bare minimum. Even Boston’s police department was reportedly not informed of what we now read was a cursory investigation by the FBI of the elder Tsarnaev in 2011.