(CNN) -- Egypt's military is the foundation of the modern state, having overthrown the country's monarchy in 1952. All four of the country's leaders since then -- Gamal Abdel Nasser, Anwar Sadat, Hosni Mubarak and now, Mohammed Hussein Tantawi -- have been army or air force officers, and the armed forces play a major role in the Egyptian economy.
Egypt's army, navy, air force and air defense force have a combined strength of about 450,000. The army, with about 320,000 troops, represents more than two-thirds of that figure, according to an estimate by the Federation of American Scientists.
Military service is compulsory in Egypt. Men between ages 18 and 30 have to serve between 12 and 36 months in the armed forces, plus nine years in the reserves.
Under Nasser's rule in the 1950s and 1960s, Egypt had close ties with the Soviet bloc and its military relied largely on Soviet arms. Sadat expelled Soviet military advisers in 1972.
After the 1978 Camp David Accords, Egypt's military became the second-largest recipient of U.S. military aid, after Israel. Washington agreed to a $13 billion, 10-year aid package to Cairo in 2007.
Egypt's defense budget takes up 3.4% of its economy, according to 2005 U.S. estimates. U.S. aid represents about 25% of that spending.
Older officers, including Mubarak, were trained in the Soviet Union, but younger ones studied in the West.
Tantawi, the head of the Supreme Military Council that took power following Mubarak's ouster last week, is a 75-year-old career infantry officer. He fought in Egypt's 1956, 1967 and 1973 wars with Israel.
Tantawi has served as defense minister since 1991 and holds the rank of field marshal.
Beneath him is Lt. Gen. Sami Hafez Enan, the armed forces chief of staff. Enan, who rose through the air defense ranks, was holding talks in Washington when the Egyptian revolt broke out in late January.
The other service chiefs are Vice Adm. Mohab Mamish, who commands the navy; Air Marshal Reda Mohamed, who leads the air force; and Lt. Gen. Abdel Aziz Seif-Eldeen of the air defense force.
Decision-making within the Defense Ministry has rested almost solely with Tantawi during his tenure. But estimates of the Egyptian military's readiness have declined since he took office, according to the military analysis site globalsecurity.org.
U.S. diplomatic cables disclosed by the website WikiLeaks include reports of dissatisfaction among mid-level officers with his leadership. In a September 2008 cable, one unidentified Egyptian said the military leaders used loyalty as the sole criteria for promotion and considered officers seen as "too competent" as threats to the government.
In a March 2008 document, American diplomats described Tantawi as a skeptic of political and economic reform in Mubarak's inner circle, calling him "aged and change-resistant."
NATIONAL AND INTERNATIONAL ROLE:
Egypt's military has historically been held in high regard by the population. Protesters who mounted anti-Mubarak rallies in Cairo and other cities welcomed its intervention and praised its refusal to fire on peaceful demonstrations.
However, Egyptian civilian analysts and academics told U.S. diplomats that the elite status that military officers have long enjoyed has diminished. As pay grades fell behind private-sector work, one observer noted that, "A military career is no longer an attractive option for ambitious young people who aspire to join the new business elite instead."
Egypt holds major military exercises, dubbed "Bright Star," with U.S., NATO and other Middle Eastern nations every two years. Egypt also has offered to train officers from the U.S.-backed Iraqi and Afghan militaries.
Egyptian forces are now largely equipped with American weapons, including M1 tanks and F-16 jet fighters, but Soviet-era aircraft and armor remain in their arsenals.
Egypt's military not only produces much of its own armaments and provisions but a wide variety of consumer goods as well.
The armed forces have become "a quasi-commercial enterprise," the U.S. Embassy in Cairo noted in the September 2008 cable disclosed by WikiLeaks. "Contacts told us that military-owned companies, often run by retired generals, are particularly active in the water, olive oil, cement, construction, hotel and gasoline industries," the cable states.
That role has led to some tensions between business leaders and the armed forces, but the military also committed its "considerable resources" to producing bread during a shortage that led to riots in early 2008, the document noted.