In a Nutshell:
The scholars generally agreed a territory is termed dar al-Islam (home of Islam) where control and sovereignty belongs to Muslims and the shari'a was implemented. Peripheral conditions were disputed and differed upon. These core conditions mean it is irrelevant if its inhabitants are mainly Muslims or not, or whether Muslims are allowed to perform aspects of Islam with the permission of disbelievers who hold power.
Islam refers to a communal way of living, a discursive tradition intimately tied to power where Muslims are expected to socially and territorially embody Islam (in dar al-Islam) - acknowledging, submitting and serving Allah.
Islam thus comprises an environment derived from revelation, adapting to and reflecting the needs of the times, where every individual chooses their way of life and freely lives by it.
The first manifestation of Islam was the Prophet's Medinah followed by the Khulafah Rashidah, Umayyads, Abbasids and the Ottomans, with Islam (the deen) being dismantled and disappearing in 1924.
The juristic discussions historically centered around the conditions as to when such polities and territories would be deemed Islamic. A consensus emerged that a territory could be called dar al-Islam (home of Islam) where control and sovereignty belonged to Muslims and the shari'a was implemented, whilst peripheral conditions were differed upon.
Abu Ḥanifa's students Abu Yusuf and Muhammed al-Shaybani were early jurists who systematised concepts of territoriality, stipulating the two core conditions mentioned above. The statements of jurists from across the schools of thought are listed below.
The fourteenth century Hanbali jurist Ibn Qayyim concluded:
قال الجمهــور: دار الإسـلام هى التي نزلها المسلمــون وجــرت عليـها أحكــام الإسلام، وما لم تجر عليه أحكام الإسلام لم يكن دار إسلام وإن لاصقها، فهذه الطائف قريبة إلى مكة جداً ولم تصر دار إسلام بفتح مكة
The jumhur of the ullama say dar al-Islam is where the Muslims go and reside and the Islamic rules are dominant. If people (the Muslims) reside in one place and Islam becomes dominant that is dar al-Islam. If however, Islam does not become dominant it is not (considered) dar al-Islam even if it is in close proximity to the state. Taa'if was so close to Makkah (at the time when Makkah was dar al-Islam) but it did not become part of dar al-Islam until it was conquered. (Kitab Ahkam ahl al-Dhimmah, Vol. 1, p. 366)
Qadi Abu Ya'la said:
كل دار كانـت الغلبة فيها لأحكام الكفر دون أحكام الإسلام فهى دار الكفر
Any country where the law is Kufr (disbelief) instead of Islam is dar al-Kufr. (Al-Mu'tamad fi Usul al-Din, p. 276)
Ibn Muflih said:
فكل دار غلب عليها أحكام المسلمين فدار الإسلام، وإن غلب عليها أحكام الكفر فدار الكفر، ولا دار لغيرهما
There are only two, dar al-Islam and dar al-Kufr. Any dar (domain) where Islamic law is dominant is dar al-Islam, and any domain where Kufr law is dominant is dar al-Kufr, there are only these two camps. (Al-Adab al-Shar'yah, Vol. 1, p. 213)
The Shafi'i scholar Al-Rafi'i argued:
دار الإسلام ثلاثة أقسام : قسم يسكنه المسلمون ، وقسم فتحوه وأقروا أهله عليه بجزية ملكوه أو لا ، وقسم كانوا يسكنونه ثم غلب عليه الكفار.
قال الرافعي وعدهم القسم الثاني يبين أنه يكفي في كونها دار إسلام كونها تحت استيلاء الإمام وإن لم يكن فيها مسلم قال : وأما عدهم الثالث فقد يوجد في كلامهم ما يشعر بأن الاستيلاء القديم يكفي لاستمرار الحكم ، ورأيت لبعض المتأخرين أن محله إذا لم يمنعوا المسلمين منها وإلا فهي دار كفر انتهى.
Dar al-Islam comprises three kinds: the first kind where the Muslims live, the second kind where the land was conquered and given to its people on payment of the jizya tribune, and the third kind where Muslims used to live before it was conquered by non-Muslims. The second kind explains that it is sufficient for it to be dar al-Islam based on it being under the conquest (seizure) of the Imam (Caliph) even if there were no Muslims in it. Furthermore, it is found in the third kind it is felt the historic (old) conquest of Islam is sufficient for the continuation of the rule..." (Dr Salim, Ahkam al-ahwal al-shaksiyyah li al-muslimeen fi al-gharb, p.31)
Sulayman bin Mohammed al-Bujayrimi states:
هي كلّ أرض تظهر فيها أحكام الإسلام - ويراد بظهور أحكام الإسلام: كلّ حكم من أحكامه، أو يسكنها المسلمون وإن كان معهم فيها أهل ذمّة، أو فتحها المسلمون، وأقرّوها بيد الكفّار، أو كانوا يسكنونها، ثمّ أجلاهم الكفّار
"Dar al-Islam is the entire land where the Islamic laws (ahkam al-Islam) appear and it is intended by the phrase "appearance of the Islamic laws" every law from its laws, or Muslims live there even if there were with them ahl al-dhimma (those protected by Muslim Rulers), or it was opened up by Muslims, or it was given to govern by the hand of non-Muslims or they were living there and were expelled by the kuffar from it." (Nihaya al-Muhtaj)
The Fatwa-e Alamgiri, compiled by the jurists during Aurangzeb's era, observes:
"Muḥammad said in al-Ziyadat: dar al-Islam only becomes dar al-Ḥarb according to Abu Ḥanifah with [three] conditions. One is the enforcement of the laws of disbelief openly and that the law of Islam is not enforced therein. Second, that it is contiguous with dar al-Ḥarb, with no city from the cities of Islam between them. Third, that no Muslim or dhimmi remains secure there under the previous amnesty that was established before the dominance of the disbelievers – for the Muslim based on him being Muslim and for the dhimmi based on the contract of Dhimmah. The materialisation of this situation can be in three ways: either the residents of dar al-Harb gain power over a land from our lands, or the people of a town apostatise and gain power and enforce rules of disbelief, or the people of Dhimmah break the contract and gain power over their land. In all cases, it will not become dar al-Harb except with the three conditions. Abu Yusuf and Muhammad said [it will become dar al-Harb] with one condition alone, which is the manifestation of the laws of disbelief; and that is [the dictate of strict] logic."
Muhammad Quhustani wrote :
"As for it becoming dar al-Harb, according to [Abu Hanifah] it has conditions.
First, the enforcement of the laws of disbelief openly, in that the ruler rules by their law, and they do not refer to Muslim judges, as mentioned in al-Bahr.
Second, it being contiguous with dar al-Harb such that there is no city from the towns of Islam between them via whom assistance can reach them." (Jami al-Rumuz)
The meaning of rules of Islam requiring enforcement is their enforcement with power and strength, not the performance of the congregation and jumu'ah with the permission of disbelievers. The rule of Islam, and likewise the rule of kufr, are both determined by considering power, not by practice.
It states in Khizanat al-Muftin:
"Dar al-Islam does not become dar al-Harb until rules of idolatry are enforced therein and it is contiguous with dar al-Harb without any Muslim city between it and dar al-Harb, and no Muslim or dhimmi remains there secure on account of the earlier amnesty, and no Muslim or Dhimmi remains secure there over his own life except by amnesty of the idolaters…"
Shihab al-Din al-Khawarzami al-Bazzazi stated:
"The lands that are in the grasp of the disbelievers today, there is no doubt that they are dar al-Islam because the rules of disbelief have not manifested there, and in fact the judges are Muslims." (Fatawa Bazzaziyyah)
The Hanafi jurist Ibn Abideen wrote:
"It states in Mi'raj al-Dirayah from al-Mabsuṭ: 'The lands which are in the grasp of the disbelievers are dar al-Islam not dar al-Ḥarb because the rule of disbelief has not manifested there, and in fact the judges and governors are Muslims, following them out of need or otherwise. Every town in which there is a governor from the side [of the Muslims], it is permissible for him to establish the jumu'ahs, eids, hadd and appoint judges because Muslims have dominion over them. If the governors are disbelievers, Muslims can [themselves] establish jumu'ah and a judge will become a judge by general agreement of the Muslims, although it is necessary for them to seek out a Muslim governor." (Radd al-Muhtar)
The Hanafi jurist Al-Jassas notes:
"According to Abu Hanifah it does not become dar al-Harb until three things come together therein: it being contiguous with dar al-Harb & nothing of dar al-Islam exists between it and dar al-Harb; second, the rule of the people of disbelief is enforced therein; and third, that no Muslim or dhimmi remains secure there [based on the amnesty granted by Muslim powers]. When these three things come together therein, it becomes dar al-Harb, and when any one condition falls short it will not be dar al-Harb."
"This is like the town of al-Qirmiti. In the view of [Abu Yusuf and Muhammad], it is dar al-Harb despite being surrounded by dar al-Islam because the rule of disbelief has become manifest therein, since they manifest the religion of Zoroastrians, fire-worship and insulting the Messenger Muhammad (saw)."
"The reasoning behind this view is that the status of an abode only relates to power and dominance and the enforcement of the rule of the religion therein. The proof for the soundness of this is that when we gain power over dar al-Harb and enforce our laws therein it becomes dar al-Islam, whether contiguous with dar al-Islam or not; the same is therefore the case with a town from dar al-Islam, when disbelievers overpower it and their rule is enforced therein, it must be dar al-Harb, and there is no sense to giving consideration to a dhimmi or Muslim remaining secure over his life because a Muslim may be secure in dar al-Harb and that will not stop it from being dar al-Harb and will not necessitate it being dar al-Islam."
Then explaining Abu Hanifah's position, he says:
"As for the reasoning of Abu Hanifah's view in giving consideration to the three things that we described, it is that when it is not contiguous with dar al-Harb and there is dar al-Islam surrounding it, the dominance has no ruling because it still comes under the force of the Muslims so is like an army of people from dar al-Harb resorting to a Muslim fort with the Muslim armies surrounding them – their acquisition of the fort would not convert the fort into dar al-Harb while the Muslim armies surround them. Similar is a city the residents of which apostatise or its residents overpower it while there are Islamic cities surrounding it – it is obvious that the force of Islam remains there because they surround them. He also considered the enforcement of laws because the place which an army has acquired from the plots of dar al-Islam, even if contiguous with dar al-Harb, will not become dar al-Harb because they are unable to enforce their rule. Similar is the Muslim army when it enters dar al-Harb – the plot they acquire will not become dar al-Islam for as long as they are not able to enforce their rules. He also considered that there not remain a Muslim or dhimmi secure over his life because being secure over his life makes the place remain in the ruling of dar al-Islam as it was, and that would prevent it from changing into the ruling of dar al-Harb."
Al-Jassas then concludes:
"I believe that Abu Hanifah only said this based on the conditions that existed in his time when Muslims fought idolaters. It was not possible according to him that a dar al-Harb could exist in the middle of the abode of Muslims, where the inhabitants apostatise and despite the armies of the sultan surrounding them remain strong and have loyal subjects. Had he seen what has happened in this time, where people are negligent of Jihad and betray one another and those in leadership are engaged in corruption and show enmity to Islam and its adherents and belittle the command of Jihad and its due, he would say the same thing as Abu Yusuf and Muhammad about a town like al-Qirmiṭi, and in fact many towns like it which we dislike to mention here." (Sharh Mukhtasar al-Tahawi, 7:215-8).
The jurists generally understood the notion of dar al-Islam as referring to a territory where Islam could be lived securely as way of life. This required offices, institutions and structures such as governors, judges, treasury, security and so on.
The twelfth century Shafi'i jurist Fakhr al-Din al-Razi has been cited by researchers to suggest he was at odds with the other jurists. He innovatively used variant terminology, conveying the same understanding above. He distinguished between the Muslims as a "community of compliance" (ummat al-ijaba) and the non-Muslim "community of mission" (ummat al-da'wa) which was called to Islam via jihad (Vol. 8, p.196). This is consistent with the notions of dar al-Islam and dar al-Harb.
No scholar claims in the land of disbelievers if one openly conducted some salient aspects of Islam based on their clear permission or based on them turning a blind eye then it becomes dar al-Islam. Whilst it is may be claimed that the 11th-century jurist al-Mawardi stated, "If a Muslim is able to practice his deen openly in a land of unbelief, that land becomes dar al-Islam" and that this dictum was repeated by later jurists such as the 16th-century al-Ramli and al-Haytami following the Reconquista in Spain, where they emphasized former Muslim lands did not revert to being dar al-kufr unless all Muslims had left thereby ceasing the deen in those territories., this is problematic as the jurists understood "practicing the deen" to mean leaving a communal way of life and not the modern notion of a personal apolitical religion.
The intent of the enforcement of the laws of Islam, which is a condition for a land to remain dar al-Islam after the disbelievers gain power over it, is that the rules of Islam can be enforced by way of strength and power.
Likewise, in dar al-Harb, enforcing laws of Islam can remove it from being dar al-Harb when it is by way of power and strength, not merely that the ruler of dar al-Harb allows the laws of Islam to be put into practice.
In conclusion, the jurists conceptualized dar al-Islam (the home of Islam) as a territory under Muslim rule, a political entity where Muslims were secure and could practice their deen as a collective. Some focused on its legal system in their wording, a territory where Islamic law prevailed under the control of Muslims, others emphasized the lifeway, wherever Muslims could practice their deen in peace and security, free from oppression and persecution.
The general agreement however remained on the underlying meaning despite the minor variations in their wordings or conceptualisations.
Dr Salim, Ahkam al-ahwal al-shaksiyyah li al-muslimeen fi al-gharb
Al-Jassas, Sharh Mukhtasar al-Ṭahawi
Fakhr al-Din al-Razi, Tafsir al-Fakhr al-Razi
Ibn Abideen, Radd al-Muhtar
Ibn Qayyim, Kitab Ahkam ahl al-Dhimmah
Imam Shihab al-Din al-Khawarzami al-Bazzazi, Fatawa Bazzaziyyah
Muhammad Quhustani, Jami al-Rumuz
Sulayman bin Mohammed al-Bujayrimi, Nihaya al-Muhtaj