The Holy verse says:
"O Prophet, urge the believers to battle. If there are among you twenty [who are] steadfast, they will overcome two hundred. And if there are among you one hundred [who are] steadfast, they will overcome a thousand of those who have disbelieved because they are a people who do not understand." (8:65)
What does the word (HARRED) which is translated to English as (urge) mean?
In Arabic (the original language of the Holy Quran) the word used is "HARRED" which is translated to "urge" but let's focus on the meaning of the Arabic word (HARRED). Arabic language has a very special way of derivation of words, making derivation has lots of cases in Arabic, this case is a very special one that shows the strength and depth of the Arabic language.
In Arabic the word (MARAD ) means disease. We can derive a word from the origin (MARAD) that means fighting or facing disease by repeating the middle letter so the derived word to mean fighting or facing disease will be (MARRAD). Similarly, the orange peel in Arabic is called (KESHR). So the derived word to mean removal of the orange peel it will be (KESHSHR). There are other ways to make derivatives that mean fighting or removal of the original word, but this is the case we need to focus on.
The word (HARRED) is derived from the origin (HARAD) which means very close to perdition. When you say that someone is (HARAD) it means he is very close to perdition. The origin word (HARAD) was used in another verse " They said, "By Allah, you will not cease remembering Joseph until you become fatally ill or become of those who perish." (12:85) the Arabic word used by the Holy Quran for "become fatally ill or become of those who perish." is (HARAD).
So the word (HARRAD) used in the verse (8:65) means in Arabic (removal of being close to perishing ). This means that the war that God is commanding our noble prophet to wage is to save the Muslims from perishing. This coincides with the historical facts that the disbelievers were conspiring against the Muslims by all possible means. So it is not actually a call to transgress, it is actually a call for self defense by fighting against those who are fighting you.
The rest of the verse explain why our noble prophet had to "urge" the Muslims to fight. They were outnumbered by the disbelievers. That's why the rest of the verse explains to them that the strength in war is not measured only by number. There is another very important factor which the power of faith. This power motivates the warrior to excel beyond his own personal expectation.
In this verse God has specified a maximum and minimum for this power as people vary in their physical and spiritual strength. The power of faith of a Muslim makes his strength range from two to ten times as strong as a disbeliever. That is because he is not as attached to life as the disbeliever . A believer knows that life is only a passage to the afterlife where he will be rewarded so dying is not that much a disaster to him.
While the disbeliever is so attached to life as he believes that if he died then he ceased to exist and will be forgotten so when he is attacked by more than one he can run or try to save himself by any possible means. That is why Khaled Ibn AlWaleed, the prominent Muslim military commander told the Persians: " I have come to you with men who love death as you love life"