In Islam Jihad is all efforts one exerts in advocacy of Islam and its society. The highest level of Jihad is fighting the enemy but God has only permitted it for three reasons. They also have to observe Islam morals. 

Jihad

The highest form of jihad is fighting the enemy. When Allah sent Prophet Muhammad (peace be upon him) as His messenger to all mankind, He commanded him to advocate the divine faith and tolerate whatever harm he and his followers might be subjected to.

The form of jihad that the Prophet (peace be upon him) was commanded to exert during the Makkan period was to recite the Qur’an to all people, make his argument and provide its proofs.

 Yet the unbelievers stopped at nothing in their enmity towards Islam and Muslims and they plotted to assassinate the Prophet (peace be upon him).

 In response to this plot Allah instructed him to migrate with his Companions to Madinah. Then Allah gave His messenger permission to fight his enemies in self defence and to give the Muslim community a secure base.

These verses justify granting the permission to fight, giving three reasons:

1-That the Muslims were unjustly persecuted and forced to leave their homeland against all right. Their enemies held nothing against them other than the fact that they  believed in the true religion, declaring that they worship none other than Allah.

2-Without granting this permission to fight, all places of worship where Allah’s name is abundantly praised and glorified would have been demolished through the injustice of those who did not believe in Allah and the Last Day.

3- The ultimate purpose of victory, and the establishment of Islam on earth, is so that people can attend regularly to their prayers, give in charity, enjoin the doing of what is right and forbid the doing of what is wrong.[1]

Then Allah made fighting a duty of the Muslims, saying:

On the basis of this verse, fighting is a duty of the Muslim community in certain situations. It is a collective duty, which means that when sufficient numbers of Muslims undertake it and are able to repel the enemy, the others are exempt. Fighting becomes a personal duty in one of four situations:

1) When the ruler calls for full deployment.

2) When a person possesses skills that Muslims lack yet need for battle, as in the case of an air force pilot. 

If the enemy attacks a Muslim city. In this case the whole population must be mobilized to fight the enemy off; and If a person who is able to fight attends happens to be on site of the battle.

3) ground when Muslims and their enemies are about to engage.

Jihad is not a duty of non-Muslims, women, children, or ill and insane persons.

Islam urges Muslims to undertake jihad, making it an important task they should fulfil to uphold Allah’s rulings and establish the divine faith. It promises that fighters will be admitted into heaven as long as they remain steadfast in fighting for the truth.

Jihad must be for Allah’s cause. If its aim is not to support Allah’s cause, then it is not jihad. Not everyone who fights a battle, claiming to be on jihad, is truly so. 

A man came to the Prophet (peace be upon him) and said: ‘Who of these fights for Allah’s cause: a man fighting to achieve war gains, a man fighting so as to gain reputation, and a man fighting so as to be recognized?’ The Prophet (peace be upon him) answered: ‘The one who fights so that Allah’s word will reign supreme, is the one fighting for Allah’s cause.’ What this hadith tells us is that a person who fights for any material or mental gain, such as enhancing his standing among his people and being described as a hero, does not serve Allah’s cause, even though he may be fighting the enemies of Islam.

Allah’s word is supreme when people are truly free, undeterred by any force from believing in the divine faith should they wish to embrace it. Islam does not compel anyone to accept it, but at the same time it does not accept that any force should stand in the way of people if they wish to believe in it. It lays down a fundamental and basic principle:

All Muslims are required to explain Allah’s message to all people. They should inform them of it and make clear what Allah wants: that they should believe in His oneness and that He has no partners. They are then left free to believe in it or reject it. They are accountable for their choice. When some power takes action to compel people to reject the divine faith, preventing them physically from believing in Allah, the Muslims must, if they have adequate means, remove such tyranny and ensure people’s freedom of choice.

This is the purpose of jihad, whether it is undertaken in self defence or in pursuit of the truth. Therefore, Islam establishes certain values and requires the Muslims to abide by them when they fight, whether they are commanders or ordinary soldiers. They set out in Allah’s name and have no purpose other than to earn His pleasure. Allah does not accept that anyone should suffer injustice. Therefore, Muslims must observe these values, clearly stated in the Prophet’s instructions to the commanders he sent out on missions and in the instructions given by his rightly-guided successors.

Human history, both recent and old, is full of cases of armies launching surprise attacks on peaceful villages and towns, killing, raping and looting. Muslim armies, by contrast, have to observe the highest moral standards of Islam. This is made absolutely clear in the letter of instructions given by the second Caliph, 'Umar ibn al-Khattab, to his army commander Sa'd ibn Abi Waqqas and his army:

I command you and your soldiers to remain God-fearing in all situations. To be God-fearing is the best support you may have against your enemy and the best plan in war. I counsel you and your soldiers to guard against all sinful actions more than you guard against your enemy. Sinful action is more detrimental to an army than their enemy. Muslims earn Allah’s support because of their enemy’s disobedience of Allah. Had it not been so, we would not be a match for them: we lack their numbers and their equipement. Should we stand on equal terms with them in regard to disobeying Allah, they will overpower us. If we cannot achieve victory through being the better side morally, we cannot win by our force alone. Learn that as you move on, you are accompanied by angels appointed by Allah, and these angels watch what you do. Therefore, remain shy of them and refrain from committing sin when you are on a mission to serve Allah’s cause [...] Pray to Allah to help you against self temptation just as you pray Him to grant you victory against your enemy. I pray Him to grant this to us and you.

These values continued to be upheld by Muslims when they fought their enemies over many centuries. History does not record a single incident of a Muslim army plundering a city, looting and killing civilians. Yet recent history, particularly in our modern times, has witnessed massacres committed in Muslim countries. However, these are perpetrated by dictators who recognize neither Islamic values nor human values and honour no covenant in their treatment of believers or unbelievers.