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The US-led coalition launched about two combat aircraft sorties per hour against Islamic State militants in Syria and Iraq at the time of publication of this audiograph in November 2015, but how does that compare to previous aerial campaigns? Neal Razzell explores comparisons with the invasion of Iraq, WW2, and Nato's bombing of Serbia in 1999.

Image: Smoke billows following a reported air strike by the US-led coalition in the area of al-Sajariyah, east of the city of Ramadi, Iraq. Credit: Getty Images
Composite with sound frequency graphic. Credit: Thinkstock