The International Institute for Strategic Studies has published its annual Armed Conflict Survey.

It says the second most lethal conflict after Syria was recorded in Mexico, where more than 20,000 people were killed in violence fuelled by the nations powerful drug cartels.

Here, Ioan Grillo, the author of "Gangster Warlords" who has spent 15 years investigating criminal networks across the region, speaks about how Mexico's situation has become so bad.