"War’s destruction of economies, public services, and the environment leads to deaths that occur long after bombs drop", wrote the report's authors.
Millions have been killed by the reverberating impacts of war following 9/11, a report has found.
Research by the Costs of War project suggests at least 4.6 million people have been killed by the direct and indirect effects of violence in the Middle East and Africa, where the US and its allies were involved in counterterrorism.
It estimated secondary impacts of fighting, such as the destruction of economies, public services and the environment, had led to between 3.6 to 3.7 million deaths, added to the 906,000 - - 937,000 people killed directly in the bloodshed.
This number is still rising.
"War’s destruction... leads to deaths that occur long after bombs drop and grow in scale over time," wrote authors from the US Costs of War Project, which is part of Brown University's Watson Insitute.
The report highlights the devastating impact of war on human life in Afghanistan, Iraq, Pakistan, Syria, Yemen, Libya and Somalia.
While these states have endured "violent wars" involving the US, authors of the report did not "attribute direct responsibility to any single combatant".
"Many warring parties and many intensifying factors have contributed to these deaths," they wrote.
Following the September 11 attacks in 2001, the US launched the war on terror to combat Islamist militants The military campaign - still ongoing - has targeted groups such as Al-Qaeda and the Islamic State, plus toppled the regime of Saddam Hussien in Iraq.
Critics have slammed the morality, effectiveness and cost of the war on terror.
These post-9/11 campaigns have displaced 38 million people - the largest number of forced displacements since World War Two - and cost €7.4 trillion, according to the Watson Insitute for International and Public Affairs
The Costs of War report, published on Monday, said the more than 4.5 million deaths in these war zones were linked to "significant causal pathways".
These included "economic collapse", leading to the "loss of livelihood and food insecurity", "destruction of public services and health infrastructure", "environmental contamination", and "reverberating trauma and violence", alongside "forced displacement".
“In a place like Afghanistan, the pressing question is whether any death can today be considered unrelated to war,” said Stephanie Savell, Costs of War co-director and author of the report.
“Wars often kill far more people indirectly than in direct combat, particularly young children.”