Again in the month of Shawwal, two years later in 5 A.H., another great war was on the rise.  The Jews allied themselves with the unbelievers of Mecca led by Abu Sufyan, the Bedouin tribes of Ghatafan, Solaim, Bani Qais and Bani Asad as well as the Jews of Khaibar to destroy Islam and its Prophet in a final escapade.

 This battle is historical in its nature and an example of the excellent defensive capabilities of the Messenger of Allah (s.a.w.).  It is known also as the Battle of Khandaq (ditch or trench) because of the innovative strategy of digging a trench fifteen feet wide and as deep along the undefended north-west edge of the city.  The enemy soon approached and were struck dumb with astonishment.  This mode of defense was unknown to the Arabs, and they were at a loss to understand how to overcome this obstacle so they laid siege.

 Madinah was besieged by 10,000 idolaters from diverse clans.  Banu Quraidah severed their peace agreement with the Messenger of Allah (s.a.w.) and joined the ranks of the unbelievers.  Thus, the balance of forces changed in favor of the enemy.  The Muslims were deeply frightened.  The Qur’an describes them saying:

 More than a fortnight elapsed, when a party of the besiegers’ horsemen found the narrowest and weakest guarded part of the ditch.  Amru bin Abd Wid, Nawfal bin Abdullah and Dzarar bin Al-Khattab, led by Ikrimah bin Abu Jahl, spurring their horses leaped forward towards the Muslims and challenged them to single combat.
 Amru bin Abd Wid, on horseback, strolled conceitedly on the other side of the trench, taunting the Muslims and taking pride in his heroic deeds.  He then shouted:  "Is there anyone among you who will challenge me in a single combat?"
 
Imam Ali (a.s.) asked the Messenger of Allah (s.a.w.) to permit him to accept the challenge, but the Messenger of Allah (s.a.w.) said:  "Sit down.  It is Amru."

 Abd Wid repeated his challenge debasing the Muslims and mocking them, saying:  "Where is your Paradise to which you allege to go if you were killed?  So, why don’t you send me a man accepting my challenge?"

 As none of the Muslims showed willingness to accept his challenge, Imam Ali (a.s.) repeated his request:  "I am for him, O Messenger of Allah!"

 The Messenger of Allah (s.a.w.) again declined saying:  "Sit down, it is Amru!"

 Imam Ali (a.s.) showed little respect for Amru and others like him, and said,  "What if he is Amru!"

 At this stage the Messenger of Allah (s.a.w.) agreed to let him go.  He gave Ali (a.s.) his own sword, Dhulfiqar, dressed him with his own armor, and put his own turban on his head, and then he said, "O Lord!  This is my brother and cousin.  So, my Lord, do not let me alone.  You are the best of inheritors!"

 Ali went to the battle-field and talked to Amru, saying:  "You had made a promise to God that no man of the Quraish would give you two courses without you choosing one of them."
 "Indeed," replied Amru,  "What is that?"
 "I summon you to Allah, His Messenger and to Islam."  Imam Ali said.
 "I have no need of that."  He answered.
 "Then I summon you to fight." said Imam Ali (a.s.)
 "Go back," he told him, "There was great friendship between me and your father, and I do not like to kill you."
 "But by Allah, I like to kill you."

 Amru became angry and darted at Imam Ali (a.s.), who faced him boldly, as usual, and killed him.  The voice of Imam Ali (a.s.) was heard heralding "Allahu Akbar" (Allah is the Greatest!) which indicated victory.

 When Imam Ali (a.s.) returned from the battlefield, the Messenger of Allah (s.a.w.) received him and said:  "The fighting of Ali bin Abi Talib with Amru bin Abd Wid is greater in measure than the actions of my people until the Day of Resurrection."

 After killing of Amru bin Abd Wid, Imam Ali (a.s.) had the gap in the trench which Amru had breached blocked, and took his post at that point with the intention of confronting anyone who might try to cross the trench.  Otherwise, the army of the disbeliever’s, with their thousands, would have invaded Madinah and beaten the Muslims. Thus, Imam Ali (a.s.) heroism in the Battle of Ahzab was the most decisive factor in victory for the Muslims, and in defeating the army of the disbeliever’s.  The death of Amru struck terror in the hearts of the enemy and they began to abandon the fight group by group.  Soon, Abu Sufyan, as well, had to retreat.

 The crushing defeat suffered by the unbelievers in the Battle of Ahzab at the hands of Imam Ali (a.s.) so shattered their power and pride that they never afterwards thought of advancing towards Medinah with any sinister design.  This battle also showed them beyond doubt that with a selfless supporter, and a dauntless warrior like Imam Ali (a.s.) to protect the Holy Prophet of Allah (s.a.w.) and his Mission, Islam had come to stay.

 Following the Battle of Ahzab, several minor wars took place in which the reputation of Imam Ali (a.s.) gained great notoriety and fear in the hearts of anyone who opposed him.  Many great warriors would refuse to face him on the battlefield and sometimes Imam Ali (a.s.) in order to put an end to a battle would disguise himself or move stealthily at night so that the enemy would not recognize him.  The battles of Banu Quraidah, Banu Mustalaeq, and Fadak are some of these