<P> Canals were dug to irrigate fields as well as provide drinking water for the people . Abu Musa canal (after the name of governor of Basra Abu - Musa al - Asha'ari) was a nine - mile (14 km) long canal which brought water from the Tigris to Basra . Another canal known as Maqal canal was also dug from the Tigris . A canal known as the Amir al - Mu'minin canal (after the title Amir al - Mu'minin that was ordered by Caliph Umar) was dug to join the Nile to the Red Sea . During the famine of 639 food grains were brought from Egypt to Arabia through this canal from the sea which saved the lives of millions of inhabitants of Arabia . Sa ` d ibn Abi Waqqas canal (after the name of governor of Kufa Sa ` d ibn Abi Waqqas) dug from the Euphrates brought water to Anbar .' Amr ibn al -' As the governor of Egypt, during the reign of Caliph Umar, even proposed the digging of a canal to join the Mediterranean to the Red Sea . This proposal, however, did not materialize due to unknown reasons, and it was 1200 years later that such a canal was dug, today's Suez Canal . Shuaibia was the port for Mecca . but it was inconvenient, so Caliph Uthman selected Jeddah as the site of the new seaport, and a new port was built there . Uthman also reformed the city's police departments . </P> <P> The Rashidun army was the primary military body of the Islamic armed forces of the 7th century, serving alongside the Rashidun navy . The Rashidun army maintained a very high level of discipline, strategic prowess and organization, along with motivation and self initiative of the officer corps . For much of its history this army was one of the most powerful and effective military forces in all of the region . At the height of the Rashidun Caliphate the maximum size of the army was around 100,000 troops . </P> <P> The Rashidun army was divided into the two basic categories, infantry and light cavalry . Reconstructing the military equipment of early Muslim armies is problematic . Compared with Roman armies or later medieval Muslim armies, the range of visual representation is very small, often imprecise and difficult to date . Physically very little material evidence has survived and again, much of it is difficult to date . The soldiers used to wear iron and bronze segmented helmets that came from Iraq and were of Central Asian type . </P> <P> The standard form of protective body armor was chainmail . There are also references to the practice of wearing two coats of mail (dir'ayn), the one under the main one being shorter or even made of fabric or leather . Hauberks and large wooden or wickerwork shields were used as a protection in combat . The soldiers were usually equipped with swords that were hung in a baldric . They also possessed spears and daggers . Umar was the first Muslim ruler to organize the army as a state department . This reform was introduced in 637 . A beginning was made with the Quraish and the Ansar and the system was gradually extended to the whole of Arabia and to Muslims of conquered lands . </P>

Important events during the period of four caliphs of islam