In Surah Al-Fath (28) Islam has been described as destined to be enforced over all other systems. This verse states: "He it is Who hath sent His messenger with the guidance and the religion of truth, that He may cause it to prevail over all religions. And Allah sufficeth as a Witness". In addition to peaceful means,the approach to get Islam enforced over other systems/din is, if required, 'Jihad bil saif', as has been mentioned in Surah al-taubah-29 which states that " Fight those who do not believe in Allah or in the Last Day and who do not consider unlawful what Allah and His Messenger have made unlawful and who do not adopt the religion of truth from those who were given the Scripture - [fight] until they give the jizyah willingly while they are humbled".
There are two types of 'Quranic' verses relating to "qattal" in terms of type of direction; first are those in which direction is in the form of "order"(e.g. al-taubah-29); second are those in which direction is in the form of "permission"(e.g.Surah Al-Hajj-39-41). The first type of verses are relating to domination/enforcement of Islam over the other systems/religions. The second type of verses are relating to self-defense; relating to Muslims who are subjected to injustice and suppression; relating to Muslims who are not ruling nation but want to establish Islamic system over themselves (all three situations may be inferred from Surah Al-Hajj-39-41). In this second type of verses, Muslims are permitted to undertake "Qattal"; the word "uzen" used in verse al-hajj-39 means "permission".
Therefore, we should not confuse "order of qattal" with "permission of qattal".The "order of qattal" is meant for domination/enforcement of Islam over other religions/systems. Whereas "permission of qattal" is meant for three situations, as mentioned above, adduced from sura al-hajj-39-41 in which Muslims may have or may not have capacity to launch "qattal". That is why in those three situations Muslims are not ordered rather are permitted to launch "qattal", keeping in view their conditions/capability. In other words, in these three situations, Muslims are permitted to launch 'qattal' if they have capability to launch 'qattal'. It may please be noted that all three situations in which 'qattal' is permitted (not ordered) pertain to non-ruling Muslim nations. It means order of "Qattal" to get Islam dominating/ enforcing over other systems does not apply to non-ruling Muslim nations (i.e. people/nation not having authority to enforce laws); rather it applies only to ruling Muslim nations (i.e. people/nation having authority to enforce laws). However non-ruling Muslim nations are permitted to wage 'qattal' in three situations i.e. for self-defense; for liberation from non-Muslim subjugation; and for establishment of Islam over themselves, if they have enough capability for success. All these three objectives/situations of 'qattal' by non-ruling Muslim nations are adduced from the situations mentioned in al-hajj-39-41.
Non-ruling Muslim nations (i.e. people/nation not having authority to enforce laws) are not ordered to wage 'qattal', if they are obstructed to establish Islam over themselves. But if Muslims are ruling nation (i.e. people/nation having authority to enforce laws) and they are obstructed by force from establishing Islam over themselves, in that case Muslims are ordered to wage 'qattal'. The Muslims (ruling nations) are, all the times, under obligation to establish Islam over themselves (surah Ale Imran-85; al-fath-28).
We may conclude that establishment of domination/enforcement of Islam over other systems, is the duty assigned to Muslims (ruling nation), and for that purpose they are ordered to launch "Jihad bil Saif". Non-ruling Muslim nations are not ordered to wage 'qattal' for domination/enforcement of Islam over other systems/'din'. However non-ruling Muslim nations are permitted to wage 'qattal' keeping in view their capability for three objectives i.e. self-defense; for liberation from non-Muslim subjugation; and for establishment of Islam over themselves.