Syria's diminished security forces

Following is a breakdown of estimated security forces loyal to Syrian President Bashar al-Assad, according to the The Military Balance 2013, published in March by the International Institute for Strategic Studies in London.

On paper the Syrian army remains one of the biggest in the Middle East, but its fighting capacity has been cut roughly in half by the country's civil war, the IISS estimates.

- Troops: The Syrian army consists in theory of 178,000 troops, including 110,000 in the army, 5,000 in the navy, 27,000 in the air force and 36,000 in air defences.

In 2009, the total number was estimated at 325,000, of which 220,000 were army troops.

"The nominal pre-war strength of the army has likely been reduced by half: the result of a combination of defections, desertions and casualties," IISS experts said.

"Most formations are now understrength. Some brigades are reported to have been disbanded because of either political unreliability or heavy casualties."

Owing to disorganisation stemming from the civil war, the IISS said it was unable at present to accurately estimate the strength of Syrian paramilitary forces, which have played a key role in the fighting.

In 2009, they were estimated at 108,000, including 8,000 in the gendarmerie, under the authority of the interior ministry, and 100,000 in the popular militia of the Baath party, which has been in power since 1963.

As regards reservists Syria's army has 314,000 troops, while there are 4,000 in the navy, 10,000 in the air force and 20,000 in the air defences.

- Structure: The ground army has seven armoured divisions in principle, three mechanised infantry divisions, two special forces divisions and a Republican Guard, created in 1976 and charged with state security.

The fighting capacity of the special forces and the Republican Guard is considered to be superior to that of the regular army.

The IISS estimates that with special forces dominated by Assad's Alawite minority, the Republican Guard and the 3rd and 4th army divisions, the regime is backed by 50,000 elite troops.

- Equipment: the army is equipped with mainly Russian-made materiel, and included 4,950 tanks when fighting began.

It has nonetheless suffered "significant losses of armour, while the air force has also lost some combat aircraft and helicopters."

Syria has a large arsenal of missiles, the command of which is based in the northern city of Aleppo.

The navy has two frigates. The air force has in principle 365, mainly Soviet-built, fighter planes. They numbered 555 in 2009.

"The level of readiness of a significant element of the air force's combat aircraft inventory is likely poor," the IISS noted.

Air defence units appear to have been the least affected by the fighting, and are equipped with several thousand Russian ground-air missiles, including some recent and potentially effective models.