Thermobaric munitions can be traced back to World War Two, when they were initially used by the German army. They were not widely developed until the 1960s, when the US used them in Vietnam.
The US also used them in Afghanistan. First, in 2001 to try to destroy al-Qaeda forces hiding in the caves of the Tora Bora mountains, and in 2017, against Islamic State forces.
Russia used them in its war in Chechnya in 1999 and was condemned by Human Rights Watch for doing so.
Russian-made thermobaric weapons were reportedly used in the Syrian civil war by the regime of Bashar al-Assad.What is a thermobaric or vacuum bomb? – BBC News