Factbox: Egypt's powerful military

Will Egypt's army protect the protesters, or the president? Bloodshed in Cairo makes a rapid decision imperative, analysts say, not least because further delay will tear at the unity of Egypt's strongest institution.

Egyptian President Hosni Mubarak's ruling apparatus has relied on the military since he came to power in 1981. All four Egyptian presidents since the 1950's have come from the military, now led by Field Marshal Mohamed Hussein Tantawi.

Here are some details of Egypt's military which totals around 4,68,500 active personnel, plus a reserve of 4,79,000.

* Army:
Numbers: 2,80,000 - 3,40,000 including conscripts.
Main Battle Tanks - 3,723, including 973 A1M1 Abrams tanks.
Reconnaissance vehicles - 410.
Armoured Infantry Fighting vehicles - 610.
Armoured personnel carriers - 4,160.
Artillery pieces 4,480 (including 492 self-propelled, 962 towed).
Mortars - 2,528.
Air Defence surface-to-air missiles - at least 2,100.
Tactical surface-to-surface missiles - over 42.

* Navy:
Numbers: 18,500 including conscripts.
Submarines - 4 tactical patrol submarines.
Surface combatants - 10
Patrol and coastal combatants - 41

* Air Force:
Numbers: 30,000 including 10,000 conscripts.
Combat capable aircraft - 461. 165 fighter aircraft including 26 F-16A, 12 F16-B, 74 MiG-21F and 53 Mirage DE.
Helicopters - 4 Commando electronic Intelligence
125 Electronic Attack helicopters                                                                                   

* Other forces:
There are also 1,50,000 Air Defence Command troops and 3,97,000 paramilitaries comprising Central Security Forces, National Guard and Border Guard forces.

* Some history:
-- The performance of the army during the October 1973 War helped restore the military's prestige after its defeat in the Six-Day war against Israel in 1967 and served to justify President Anwar Sadat's emphasis on professionalism instead of involvement in civilian politics.

-- The armed forces have played a role in maintaining domestic stability previously, although only under the most compelling circumstances. These included the violent 1977 food riots and an uprising of conscripts of the Central Security Forces in Cairo and other cities in 1986.

-- The professionalism Egypt's forces, demonstrated during these emergencies, reinforced a public perception that the army was the ultimate safeguard against militant Islamists or others who might threaten civil authority.

Sources: ReutersIISS Military Balance 2010globalsecurity.org.