The Messenger (PBUH) ordered the manufacture of the catapult and the armored car. Al-Bayhaqi mentioned in the Sunan that Abu ‘Ubaydah (ra) said:. “Then the Messenger of Allah put siege around Tai’f, and erected the catapult against them for seventeen days”. Abu Dawud reported in the al-Marasil from Makhul “That the Prophet (PBUH) erected the catapult against the people of Ta’if”. Al-San’ani said in Subul al-Salam that its narrators are reliable. The author of the Sirah Halabiyyah said: “It is Salman al- Farsi (ra) that directed him to do this. He said, ‘In Persia we used to erect the catapults on top of the castles and hit our enemy.’ It is said that Salman (ra) made it with his own hands”. Ibn Al-Qayyim reported from Sa’d ibn Al-Mu’adh and Ibn Hisham in Ibn Ishaq’s Sirah: ..

“Till the day of shatter took place near the wall of Ta’if, few people of the companions of the Messenger of Allah (PBUH) moved under an armored car and entered the wall of Ta’if so as to burn it. Thaqeef sent against them rods of iron heated with fire, so they got out of it. Thaqeef then hit them with arrows and killed some of them”. Thus, Salman was the one that advised them about the use of the catapult, and it is said that he made it with his own hands. .

This must have been done by the command of the Messenger (PBUH). You can find in the seerah, the saying of al-Halabiyyah: “he directed him to it”. This means he advised the Messenger (PBUH) of that. It is understood from these reports that military industries are of the responsibility of the Khalifah, and he seeks the help of whomever he likes to undertake them and organise them. The industry does need an amir, rather than a manager. Salman was not an amir to the military industries, rather a manager to the catapult industry; and he may have worked with his own hands. Establishing the military industries is compulsory, because of His (PBUH) saying:. “Make ready for them all you can of (armed) force and of horses tethered, that thereby you may dismay (place terror in) the enemy of Allah and your enemy, and others beside them whom you know not. Allah knows them.” [TMQ 8:60].

This terror cannot take place without preparation, and preparation requires the presence of factories. Thus the verse indicates the obligation of establishing the military factories through the meaning of necessity (dalalat al- iltizam), or based on the rule that states (whatever is necessary to fulfil an obligation is itself obligatory). This is besides the evidences that oblige jihad, which indicate by necessity the obligation of establishing factories. .

The establishment of factories by the State are not confined to only military factories. There are rather other factories that the state must establish, which came in the book of ‘the funds in the Khilafah State’ and are as follows: .

The factories: The state must establish two types of factories based on the obligation upon the State to look after the interests of the citizens: .

The first type: The factories that are related to the assets of the public property such as the factories used in extracting, purifying and melting the minerals, and the factories of extracting and refinery of oil. These types of factories are of public property because of the material they produce. Since the assets of the public property are public property to all Muslims, then their factories are publicly owned by all Muslims, and the State establishes them on behalf of the Muslims. .

The second type: The factories that are related to the heavy industry and the weapons industry. These types of factories are allowed to be owned by individuals because it is of the individual property. However, such types of factories and industries need huge funds, which individuals can not often finance, and the heavy industry nowadays does not cater for weapons owned by individuals, as was the case in the time of the Messenger (PBUH) and the time of the Khulafaa’ Rashidun. They rather became owned by the State, and the State works on providing them, because the duty of caring obliges it to do so. This is particularly true considering the vast development of weapons, and the expense in running the required manufacturing facilities... Therefore, it is obligatory that the State establishes factories for manufacturing weapons, and factories for the heavy industries. However, this would not mean preventing the individuals from establishing these industries. These factories are obliged upon the State to establish, i.e. they are the duty of the Khalifah. He appoints to them a general manager linked directly to him, or to his deputy, choosing the one he prefers.