The above video shows the first recording of cluster submunitions in the Syrian conflict, designated AO-1Sch. The video was filmed on July 10th 2012, and until October 2012 it was one of two examples of cluster bomb use in Syria.
Originating in the former-Soviet Union, AO stands for “Aviatsionnaya oskolochnaya”, or "Aircraft fragmentation". These are anti-personnel munitions, dropped in RBK-250/RBK-250-275 cluster bombs from aircraft, with each cluster bomb carrying 150 AO-1Sch bomblets. The majority of these cluster submunitions that have been recorded in Syria were manufactured in the 70s and early 80s, with a few recent examples showing manufacturing dates of the late 80s. Large numbers of unexploded submunitions have been recorded, possibly because of their age and the degradation of the mercury based detonator.
After their first isolated recorded appearance in July 2012 they reappeared in October 2012 when large numbers of videos started appearing online from across Syria showing unexploded cluster submunitions. These videos appeared shortly after a major highway was closed by fighting in Idlib, and it's possible the escalation to the use of cluster bombs was a response to that.
Much like the AO-1Sch, this is another Soviet-era munition dropped in groups of 30 inside a RBK-250/RBK-250/275 cluster bomb. These larger submunitions are designed primarily as anti-vehicle weapons.
The above video shows their first appearance in Abu Kamal, on the Syrian side of the Syria/Iraq border in August 2012, and it is a good example of the handling of unexploded cluster submunitions that has been seen repeatedly in the conflict. The problem with unexploded ordnance (UXO) is there's no way to know if they are safe to handle, and could detonate at any time.
As with the AO-1Sch submunitions this isolated incident of their use was followed by their use across Syria from October 2012 onwards. Along with the AO-1Sch submunitions they are the most commonly recorded type of explosive submunition used in the conflict, with hundreds of videos of their use posted online.
In November 2012 a new type of cluster submunition appeared in the conflict, the ZAB 2.5 incendiary submunition. A Soviet submunition dropped from RBK-250/RBK-250-275 cluster bombs, this submunition is designed to destroy hangers, warehouses, and other large military structures.
These submunitions have frequently been described as "white phosphorous", when they are actually thermite based weapons, which is extremely difficult to extinguish. Three types of ZAB 2.5 submunitions are used in each cluster bomb, with two types containing a bursting charge that cause the bomblet to explode some time after ignition, discouraging attempts to extinguish it, and spreading the burning thermite over a wider area.
After AO-1Sch and PTAB-2.5m submunitions the ZAB 2.5 is the 3rd most commonly recorded submunition in the conflict.
In December 2012 activists began posting videos of 122mm rockets, launched from BM-21 Grad multiple rocket launchers. This particular type was the Egyptian Sakr 18/Sakr 36 cluster munition rocket, each carrying 72 or 98 submunitions respectively.
In the above video you see both the rocket, and the submunitions, which have a distinct white ribbon attached. When the rocket breaks open and releases the submunitions these ribbons cause the submunitions to start spinning, stabilising their descent. As this is happening the ribbon pulls out an arming pin, but in some instances this doesn't happen, so they landed unarmed. What can happen then is someone can come along, see the ribbon, and pull at it, arming the submunition, and causing it to instantly explode, killing anyone nearby.
While they continue to be used in the conflict they have not been recorded on as wide a basis as the AO-1Sch, PTAB-2.5m, and ZAB 2.5 submunitions.
A rarer type of submunition appearing in March 2013 was the ShOAB-0.5, another Soviet-era submunition, this time dropped from the larger RBK series bomb, the RBK-500. A copy of the American BLU-26, hundreds of these are carried in the RBK-500 cluster bomb, with each submunition carrying hundreds of metal ball-bearing, creating a devastating anti-personnel weapon. So far only a handful of videos showing these submunitions have been posted online.
This 6th type of submunition was only recorded once in May 2013, and has a slightly different delivery method from other air-dropped cluster submunitions. The submunitions are carried in containers, and then released in batches, allowing them to be dropped in long lines, ideal for attacking convoys. So far no other videos of these submunitions have been posted online.
The latest submunition only appeared in June 2013 in Harbnafeh, Hama. These types of cluster submunitions can be both dropped inside RBK series cluster bombs, as with the PTAB 2.5m or AO-1Sch types, or inside a KMGU/KMGU-2 container, like the PTAB 2.5KO bomblets. So far there's only one example of these cluster submunitions recorded in the conflict.