Dhul Qarnain~ means the bearer of (Dhul) two (Qarnain) horns. It’s not that the person have physical horns grown out of his head, it represent the concept that the helmet or the crown that he wears had these horns attached to it ,which became his identity Dhul Qarnain.
Allah (SWT) says: we establish him in the earth; and we gave him every single matter up way in the path (means: we eased his affairs in every matter)
He was not the prophet of Allah (SWT), but he was a blessed person. As scholars write about Dhul Qurnain that he was a great King of his time, Allah gave him physical strength, means as a person he has more muscle strenght then normal man, he can lift, move and carry big things , and he also possesses a biggest army that no one can stand and face it, at that time.
Another thing that Allah (SWT) blessed him with, that he was popular amongst his people; and every one in his kingdom loves him, praise him, and they feel secure in this kingdom. He was very righteous and pious man, he worship Allah, and he has complete believe in “Tuheed: (oneness of Allah).
He decided to spread this Tuheed around the known civilization, whatsoever discovered at that time on face of earth. The scholar said that he conquered the all the land that were discovered, or as far as in his reach he conquered entirety and spread the message of Tuheed where ever he goes. This was his mission.
The story of Dhul Qurnain
When Dhul Qarnain took the mission to spread the Tauheed, he begins to travel around, and where ever he goes he conquer with the blessings of Allah (SWT), and he establish Tauheed. He was so powerful that when enemies heard that Dhul Qarnain is coming, they surrender just from the fear of his attack; this was the power Allah (SWT) blessed him with.
When he reaches the far side where the sun sets in mercury water, means he reach to the end of land near sea to the west, and mercury waters according to scholars might black sea or some believe its Algerian sea, Allah knows best.
On that land he found people; it was revealed to him: O Dhul Qarnain; Do you want to punish them or do you want to leave them in goodness. it was a choice revealed to him. (As for the one who wronged himself, he will be taken back to his lord and he will be punished him with punishment unheard off; as for the one who believes and do the righteous deeds then he will get good rewards and saved from punishments).
Then Dhul Qarnain decided to set the course towards east; he traveled until he reach where the sun arise from. Africa or Asia there are difference in opinions of scholar, but he reach some place in east, Allah knows best.
He found uncivilized people over there. These people were very primitive in knowledge that they still don’t know how to build shelter to protect them self from the sun. Basically what Dhul Qarnain discovered in the Far East were savages.
Dhul qarnain change his direction and reach Turkmenistan; He touches the mountain range of Turkmenistan. Beyond those mountains he found people, who speak a different language, they were very difficult to communicate, at that time.
Allah blessed Dhul Qarnain with Knowledge, he soon discovered a way to understand there language; not completely but enough to arrange a meaning out of it. When he crossed the barrier of communication the people came to him.
The people said: O’ the possessor of two horns, the two tribes Yajuj and Majuj creating a lot of trouble in the earth, can we pay you the fee, so that you can build a barrier between them and us. Dhul Qarnain replied: i do not need your money, what Allah has given me is enough.
Ddhul Qarnain asked them that although he will need man power to build this barrier if you want me to help you and stop the tribes of Yajuj and Majuj. Help me with all of your strengths, like people, resources and wealth to build this wall.
Dhul Qarnain said: give me blocks of Iron; his plan is to melt it down and put it between two mountains. He constructed large furnaces, and he said to below in these furnaces so that fire can melt down the iron and it became molting lava, then he mixed copper in that molting iron. He then created the wall with this compound of Iron and copper, and he told those people that this is the mercy from my lord Allah (SWT).
According to the Hadit: every single day Yajuj and Majuj are trying to get out of that wall or trying to pass through that wall, and every time they dig, and came back to it after the day it became more thicker. One day when one of them dig it by say the words In shaa Allah, then they will pass through this wall.