He will have to fight in the above two cases because the Jihâd therein will be regarded as Defensive Jihâd (Jihâd Difâ') not Offensive Jihâd (Jihâd Talab). If he were to turn away from such, the enemy may deny the Muslims of their rights and therefore maltreat them.
'When you are commanded (by the ruler) to set out (in Jihâd), go forth.' (Al-Bukhâri and Muslim).
Allâh the Majestic said:
'When you meet (an enemy) force, take a firm stand against them [Al-Anfaal: 45].
Allâh the Majestic also said:
'O You who believe! What is the matter with you, that when you are asked to march forth in the Cause of Allâh you cling heavily to the earth? [Taubah: 38].
Shaykhul-Islâm Ibn Taymiyyah may Allâh bestow His mercy on him said:
Jihâd can be with the hand; so also there is a type of Jihâd by the means of call (that is, Da'wah), (providing) proofs, (the use of) tongue, intellect, reflecting, and proficiency; this kind of Jihâd is imperative, according to the highest possible means. It is also imperative on those who are not out to fight to reciprocate that with doing goodness to the families and property of those who have gone out.' [Al-Ikhtiyaaraat Al-Fiqihiyyah p. 447].
It is obligatory on the ruler to observe his army carefully before they set out on Jihâd. He should stop whoever is not capable among men, even among the horses (nowadays, the weapons must be appropriate), among other things. Among the people he should stop from being part of the army is anybody with treacherous attitude who can affect other people with his treachery, so also is anybody with any cowardly disposition who can make the mujahedeen develop cold feet in battles. So also is any person that may transmit information about the mujahedeen to the enemy; he too should be removed from the Islamic army, or any person that may cause confusion in the ranks of the Muslim warriors. The ruler should appoint for the Islamic army a leader (Amir) who can administer the affairs of the mujahedeen according to the politics of the Shariah.
The mujahedeen must obey the leader (appointed by the ruler of the Muslims) in goodness; they must be committed to him, patient with him. The proof for all this is the statement of Allâh the Majestic:
O you who believe! Obey Allâh and obey the Messenger, and those of you (Muslims) who are in authority [Nisâ: 59]
Jihâd is legislated in Islam for attainment of lofty goals and noble aims.
Allâh legislated the concept of Jihâd to free the slaves from servitude to false-gods and idols, for worship of Allâh Alone without ascribing partners with Him. It is Allâh that created and it is He that provides for His slaves.
Allâh the Mighty said:
And fight them until there is no more Fitnah (disbelief and polytheism: i.e. worshipping others besides Allâh) and the religion (worship) will all be for Allâh Alone. [Al-Anfaal: 39].
Allâh also legislated the concept of Jihâd to remove oppression and to take back the rights to their owners. Allâh the Majestic said:
"Permission to fight is given to those (i.e. believers against disbelievers), who are fighting them, (and) because they (believers) have been wronged, and surely, Allâh is able to give them (believers) victory. Those who have been expelled from their homes unjustly only because they said: "Our Lord is Allâh." [ Al-Hajj: 39-40].,
Allâh legislated the Jihâd to bring ignominy (and disgrace) upon the infidels, punish them and weaken their strength. Allâh the Mighty said:
Fight against them so that Allâh will punish them by your hands and disgrace them and give you victory over them and heal the breasts of a believing people. And remove the anger of their (believers') hearts. Allâh accepts the repentance of whom He wills. Allâh is All-Knowing, All-Wise. [At-Taubah: 14-15].
As a condition for fighting, the enemy must have been invited (to believing that Allâh is One, then to carry out other Pillars of Islam) this was how the Messenger of Allâh SallaLlâhu alahy wa sallam used to invite people to Islam before fighting them. He would write letters to the kings and would tell the leaders of the Muslim warriors that they should first invite people to Islam before fighting them. If the people answered them good otherwise they would be fought this is because the purpose of fighting in Islam is to remove unbelief and polytheism (from Allâh's land), and to make the people embrace the religion of Allâh, thus if the latter occur without fighting then there is no need for fighting. Allâh knows best.
Jihâd has various rules guiding its execution as can be found in the well-explained voluminous works of the Scholars.
For instance if the parents (or one them) of the would-be mujâhid were in need of their son's service, the son cannot partake in a voluntary Jihâd except with their permission. The Messenger of Allâh SallaLlâhu alahy wa sallam said (to the son who wanted to partake in a Jihâd but whose parents were alive that):
'Strive to serve them ' [At-Tirmidhî regarded the hadith to be sound]. The above is so because doing goodness to both parents is an individual obligation, and Jihâd, a communal obligation. The principle is 'an individual obligation takes precedence over a communal obligation.'
(In the cause of the Jihâd,) it is not permissible to kill children, women, clergy people, old men near death, people with permanent sickness, blind people who are daft who do not take part in the fight one or the other. Those people are better taken (by the Muslim warriors) as slaves in captivity. It is permissible for the ruler of the Muslims to enter into a treaty with the infidels, as may be necessary, upon such terms as non-hostility for a given period of time. An example of that is when there is a benefit in entering into the treaty perhaps because of weakness of the Muslims wherein delaying Jihâd will be appropriate; but when the Muslims are in a position of strength and can carry out the Jihâd, there may be no need for a treaty with the infidels.
[The infidels which the Muslim state has a treaty with are called mu'aahaduun (sing. mu'aahad), and it is a grave offence to kill any of them; said the Messenger of Allâh SallaLlâhu alahy wa sallam :
'Whoever kills a mu'aahad (a non-Muslim under a treaty with the Muslim state) will not smell the fragrance of Jannah, and the fragrance of Jannah can be smelt from a distance of forty years' (al-Bukhâri: 3166.)]
[Shaykh Uthaymeen may Allâh bestow mercy on him said in Shar'h Fat'hi Dhil-Jalaal (p.521):
'Al-Mu'aahad is the person we have entered into an agreement of no-fighting with; they are of three types: Al-Must'aman (an example is a non-Muslim trader who comes to the Islamic state, the diplomatic corps of a non-Muslim state in an Islamic country, a seeker of knowledge, etc.), Dhimmi (a Christian, a Jew or a Majoosee living under an Islamic state and paying his security tax, Jizyah to the Islamic state) and a Mu'aahad (an enemy state which the Islamic state has a non-hostility agreement with).' End of quote.]
[There is an implied contract between Muslims and non-Muslims that happen to live in a country where there is no Islamic rule that they will not hurt one another. Hence, it is not permissible for any Muslim to hurt a non-Muslim living in a non-Islamic state otherwise there will be chaos. That is the view of our Shaykh, Ash-Shaykh Sharaf Raaji may Allâh preserve him].
[Continued Shaykh al-Fauzaan in Al-Mulkhas:]
The Prophet SallaLlâhu alahy wa sallam indeed had a treaty with the unbelievers at Hudaybiyyah, so also was his treaty with the Jews in Madeenah.
If the Muslim ruler however fears treachery from the infidels, he should announce the end of the treaty with them before he fights them. The proof for that is the Word of Allâh the Majestic:
If you fear treachery from any people throw back (their covenant) to them (to be) on equal terms. Certainly, Allâh likes not the treacherous. [Al-Anfaal: 58].
The meaning of the Verse is: 'Announce the end of the treaty such that you and they will be aware of the development.'
The Muslim ruler can also grant security to the People of the Book (the Christians and Jews) and the Majoos (the Zoroastrians) [in the Islamic state]. The implication of that is that they can be allowed to practise their religion upon the condition that they will pay Jizyah (security tax) to the Muslim state and will adhere to the rulings of Islam (such as not engaging in illicit acts like drinking liquor, gambling, fornication, etc.). The proof for that is the statement of Allâh the Majestic:
Fight against those who believe not in Allâh, nor in the Last Day, nor forbid that which has been forbidden by Allâh and his Messenger and those who do not acknowledge the Religion of Truth (i.e. Islâm) among the People of the Scripture (Jews and Christians), until they pay Jizyah with willing submission, and feel themselves subdued. [At-Taubah: 29].
[The non-Muslims living under the Islamic state are called Ahlu Dhimmah (People under Protection of the Muslim State), for further reading on the rulings pertaining to them, you can read Ibn Qayyim's Ahkaam Ahlidh-Dhimmah].
[Said Ash-Shaykh Al-Fauzaan in Al-Mulkhas:]
Jizyah is the wealth taken from them indicating subjugation over them. It is collected from them annually for them to replicate the Muslims not fighting them and allowing them to stay in the Islamic country (each Dhimmi has to bring the tax with his hand to the government department responsible for the collection of the Jizyah).
Jizyah is not to be taken from children nor women nor mad people nor people with permanent ailment nor old men close to their death nor blind people without power of reasoning nor poor people who cannot pay it.
[End of quoting from Al-Mulkhas Al-Fiq'hee pp. 263-267].