For all the attention given to the issue of chemical weapons in Syria the fact remains that the overwhelming majority of deaths and injuries - especially civilian deaths and injuries - are caused by conventional weapons.
Many of them - like the barrel bombs reportedly used again in Aleppo by Syrian government forces during recent days - are home-made, relatively crude and totally indiscriminate in their impact.
The barrel bomb is essentially a large, home-made incendiary device. An oil barrel or similar cylindrical container filled with petrol, nails or other crude shrapnel, along with explosives. With an appropriate fuse, they are simply rolled out of a helicopter.
The first recorded use of such weapons goes back to late-August 2012.