The Motives of the Wars of the Prophet
The Idology of International Understanding
The battles of the Prophet of Islam against the infidels were, needless to say, meant to remove those brutal selfish pagans from the scene who for the sake of their own satanic passions and desires inflicted all kinds of oppression against God's pure creatures and prevented the promulgation of Islamic precepts and beliefs. He only fought to bring about conditions of justice and equity under which human beings could materialize the ideology of world peace and mutual understanding.
Can such a war be considered illegitimate and unjust? It goes without saying that such struggles are necessary and that no Prophet could avoid combating those who intend to bring ruin on human societies and cause corruption and social decay. No doubt any wise, humanitarian person accepts such combat and admires it because there is no other way to achieve the sacred ends of the Prophets.
Jesus Christ, peace be upon him, had a short prophetic life and lived under conditions that did not permit war, so he did not attempt any wars. Otherwise, he too would have destroyed the weeds and troublemakers of human society.
Christian propaganda purposely misinterprets the holy wars of the Prophet of Islam and ascribes large numbers of casualties to them to weaken the morale of Islamic nations, to hinder the ever-increasing expansion and prevalence of Islam, and to make the murder of millions of innocent people by the masters of churches and in the crusades appear trivial and negligible to the people of the world.
Here we will first point out the motives of the Prophet of Islam in the wars he undertook, and then we will briefly cite the casualties of all the wars at the time of the Prophet, so the truth may be made clear. In this way, readers can realize the philosophy of Islamic wars for themselves and can also see that the casualties of these holy wars were trivial in comparison with those of other wars.
The War Of Badr
For 13 years after the advent of the prophetic mission of the Prophet of Islam, he and his followers were tormented and tortured by the infidel Quraysh in Makkah. Finally, the Prophet of Islam left Makkah and migrated to Medina. Yet the infidel Makkans did not stop tormenting the Muslims who had remained in Makkah and also did not let them leave Makkah and migrate somewhere else. 
At the same time, the Makkan enemies of Islam had decided to put Medina under a -severe economic siege. They had forbidden all caravans from carrying provisions and foodstuffs to Medina. This siege lasted such a long time that the people of Medina were faced with many troubles and hardships and had to go as far as the coasts of the Red Sea to buy foodstuff." 
Abu Jahl, too, wrote an extremely harsh and rude letter to the Prophet of Islam and in that letter warned him to expect the attack of the Quraysh. 
It was on this occasion that God said, 'Those who have been expelled from their homes without a just cause except that they say, "Our Lord is God." Had there not been God's repelling some people by others, certainly there would have been pulled down cloisters and churches and synagogues and mosques in which God's name is much remembered,' and surely God will help him who helps His cause; most surely God is strong, mighty' (22:39-40).
In the second year of the Hijra, the Holy Prophet of Islam arose to guard Islam, to defend the basic rights of the Muslims, and to frustrate the satanic conspixaicies of the Quraysh. In the war of Badr, they confronted the Quraysh troops. Though the number of Muslim combatants was one-third that of the infidel forces, the Muslims defeated the infidels by their power of faith and by God's help. 
The War Of Uhud
Since a considerable number of the infidel troops had been killed in the Badr war, the next year, the third year after the Hijra, the Quraysh prepared for war to take revenge for their defeat in the Badr war. They proceeded to Medina. They faced the army of Islam in a place called Uhud. Since a number of the Muslims in the war did not fully obey the instructions of the Holy Prophet, the Muslims did not become victorious in the Uhud war." 
The Ahzab (Trench) War
In the fifth year of the Hijra, a Jewish tribe called Bani Nazir went to Makkah and incited the Quraysh against Islam and the Muslims. The Quraysh took advantage of the opportunity, gathered a huge army from different anti-Islamic groups, and started toward Medina.
To guard Medina, the headquarters of Islam, the Muslims dug moats all around the city and lined up in front of the enemy army, whose number amounted to 10,000. 'Ali, peace be upon him, overcame and defeated their commander, and finally the war ended to the advantage and victory of the Muslims." 
The Bani Qurayzah War
The Bani Qurayzah  had concluded a peace agreement with the Holy Prophet of Islam, but they violated that agreement in the war of Ahzab and rendered help to the Quraysh.  Since the Prophet had recognized them as a 'dangerous' people, the Muslims had no choice but to kill them.
After the war of Ahzab, the Prophet ordered his army to proceed against the Bani Qurayzah. For 25 days, the Bani Qurayzah were besieged by the Muslim army, and they finally surrendered.
The Aws tribe asked the Holy Prophet of Islam to forgive them and spare them the punishment of death. He asked them, 'Are you ready to select Sa'ad Ma'az, who is one of the men of status among you, as the arbiter and accept his arbitration?' They all agreed, hoping that Sa'ad would take their side. But Sa'ad Ma'az's verdict was to kill their fighters, to take their possessions as booty, and to take their women captive.
The Holy Prophet said, 'The arbitration of Sa'ad Ma'az is the same arbitration God has passed upon such people'. Then all their fighters were killed. 
The Bani Mustalaq War
The Bani Mustalaq were a group of the Khaza'ah tribe who took measures against the Muslims. The Holy Prophet of Islam came to know their plots and proceeded against them with his combatants to repel their brutal assault, fought them in a place called Marisa, and defeated them. This war occurred in 6 A. H. 
The Khaybar War
Large numbers of Jews lived in the Khaybar forts and had military and economic relations with the infidels. Since the security of the Muslims was constantly threatened by those anti¬ Islamic Jews, in 7 A.H. the Muslims started towards Khaybar, which was the headquarters of the enemy, surrounded the fort, and, after a triumphant war, made the Jews submit to the Islamic government. 
The Mutah War
In 8 A. H., the Holy Prophet of Islam sent Harith ibn Umar with a letter to the king of Basra, but his messenger was killed in a place called Mutah.  At the command of the Prophet, the army of Islam marched towards the enemy, and in Mutah they confronted the army of Marqal, the king of Rome. His army comprised 100,000 Roman .and non-Roman fighters. A war broke out between the two armies in which Zayd ibn Harith, Ja'far ibn Abi Talib, and Abdullah ibn Rawahah, the three famous commanders of the army of Islam, were martyred, and the Muslims could not overcome the infidels, so they returned to Medina. 
The Conquest Of Makkah
In the Hudaybiyah peace agreement, the Quraysh had promised the Holy Prophet of Islam not to transgress against or oppress the Muslims and their confederates, but they violated the agreement and helped the Bani Bakr tribe to destroy the Khaza'ah tribe, which was one of the confederates of the Muslims. To hamper their aggression, the Prophet approachedMakkah in secrecy, entered it through an elaborate device, and conquered the city. Then he made a pilgrimage to God's House, - the Ka'aba - and delivered a historic speech in which he declared, 'You should beware that you have been bad neighbours for God's Prophet.
You refuted us, tormented us, expelled us from our homeland, and yet did not content yourselves with so much torture and troublemaking; you even did not let us have peace in Medina and attempted to fight us. But in spite of all this, I set you all free and let you go unpunished'. 
This great tolerance and forgiveness brought about the submission of the people of Makkah to Islam. In this triumphant battle, the Prophet ordered the Muslims not to fight for any reason other than defense and against the violations of the infidels. However, he passed a death sentence upon eight men and four women, and conflict arose between the army of Khalid and a number of infidels who had fought under the leadership of Akramah ibn Abu Jahl in which a number were killed. 
Hunayn And Ta'if
The Havazin tribe had gathered an army against Islam. The Holy Prophet was informed of their satanic intentions and mobilized 12,000 Muslim soldiers to confront them. The two opposing armies fought each other in the valley of Hunayn, and finally the Islamic army defeated the army of the infidels and subdued them. 
After this victorious war, the Prophet attempted to fight the Saghif tribe, who had conspired with the Havazin against Islam, but after having besieged it for a while, he dispensed with its conquest and returned to Makkah." 
Some other less severe wars also took place between the army of the Holy Prophet of Islam and the infidels, and also several journeys for the propagation of Islam were made during these blessed times.
Now the data on casualties, from both the Muslim army and the infidel's army, of all the wars that took place between the Muslims and the infidels are presented, having been gathered from credible documents.
It goes without saying that, in comparison with the casualties in the crusades of the Christians, those of the Islamic wars against the infidels are trivial, and lalso there is no doubt, therefore, that none of the wars of the Holy Prophet of Islam were launched out of motives of expansion, revenge, or aggression. Rather, they were aimed at the replusion of the aggressors, defense of the honour of the Muslims, and independence and the exaltation and prevalence of right, truth, and justice.
A Frenchman relates, 'While Islam has made it incumbent upon Muslims to make jihad, it has ordered Muslims to treat the followers of other faiths with tolerance, justice, and remission and has given them freedom of religion'. 
. Bihar ul-Anwar, Vol. 19, p.143.
. Muhammad sitari kih dar maccih dirrakhshid, p.92.
. Bihar ul-Anwar, Vol. 19, pp.265-266.
. Kamil, Vol. 2, p.118; A'lam Alwari, p.76.
. Tabaqat, pp.27-29.
. Tarikhi Tabari, Vol. 3, pp.1463-1476.
. A Jewish tribe residing near Medina.
. Bihar ul-Anwar, Vol. 20, p.191; Tarikhi Tabari, Vol. 3, p.1472.
. Tarikhi Tabari, Vol. 3, pp.1487-1493.
. Kamil, Vol. 2, p.192; Tarikhi Tabari, Vol. 3, p.1511.
. Kamil, Vol. 2, p.216; Tabaqat, Vol. 2, pp.77-78; Tarikhi Tabari, Vol. 3, pp.1575-1584.
. A place near Damascus.
. Tabaqat, Vol. 2, pp.92-94.
. A'lam Alwari, pp.104-112; Bihar ul-Anwar, Vol. 21, p.106.
. Kamil, Vol. 2, pp.247-250.
. Bihar ul-Anwar, Vol. 21, p.149.
. Sirihi ibn Hisham, p.482.
. Tamaddun, p.148.
Taken From: A Glance at the Life of the Holy Prophet of Islam , by Dar Rah Haqq's Board of Writers , Translated by: N. Tawheedi