Ahimsa Parmo Dharma - Ahimsa means non-violence, Parmo means greatest and Dharma means duty or religion. Some Indian schools of thought e.g. Buddhism, Jainism and some sects of Hinduism preach Ahimsa as Parma Dharma i.e. the greatest Karma a person can do. In the modern days, Mohandas Karamchand Gandhi popularly known as Mahatma Gandhi popularized this concept of Ahimsa Parmo Dharma a lot. Gandhi was so obsessed with this concept of Ahimsa Parmo Dharma that he went as far as calling Siri Guru Gobind Singh jee 'a misguided patriot" because Guru Sahib lifted sword to stop aggression.
A Gursikh then questioned Gandhi if he firmly believed in Ahimsa Parmo Dharma concept and if he also believed in Siri Krishna at the same time. When Gandhi replied in the affirmative, he asked him how he can believe in Siri Krishna who took part in the bloodiest battle of Mahabharata and instigated Arjuna to fight. Arjuna did not want to fight his cousins for the sake of kingdom and dropped his Gaandeev (his special bow) but Siri Krishna convinced him to fight. Their dialogue at that time is preserved as Gita. Otherwise too Krishna had numerous battles all his life. Similarly, Rama and Lakshmana hardly led a non-violent life. Same can be said of other Avatars of Hindus. Gandhi had no reply to this question and went as far as saying that Mahabharata was actually the evil war going on within. Someone should have asked him, if Mahabharata was just an internal war, then Gita that he revered so much too must have been an imagination of Rishi Beas.
Gurmat does promote Ahimsa but does not promote blind following of Ahimsa in all cases. To blindly follow the concept of Ahimsa without regard to self-respect, safety of common people is purely impotence that our Guru Sahib did not believe in.
How does Gurmat promote Ahimsa?
What causes the Himsa (violence)?
Ahimsa is mainly caused when the Jeev (creature) comes under the influence of one of the 5 vices – Kaam (lust), Krodh (anger), Lobh (greed), Moh (worldly attachment) and Ahankaar (pride). Failure in Kaam leads one to get angry and use violence in form of sexual assault to satisfy one's Kaam. If one's pride is hurt, it leads one to become angry and use violence against the person who may have instigated the hurt to one's pride. Greed of money can lead one to use violence to attain worldly wealth. If one is blinded by Moh, one may get violent for the sake of false relations. Basically, Himsa (violence) is caused by these 5 vices and such violence is strictly prohibited in Gurmat in the name of Jee-Daya (compassion for living beings).
Gurmat teaches us to be free of the 5 vices and not come under their influence. A Gursikh who indulges in chanting Gurmat Naam and obeying other teachings of Guru Sahib, is protected from the five vices and naturally stays non-violent. Gurmat teaches us to not fight or use violence to satisfy one's selfish needs.
How does Gurmat not promote Ahimsa?
Gurmat does not promote such Ahimsa that makes one an impotent unable to fight aggression.
Gurmat does not promote such Ahimsa that results in desecration of religious places, and atrocities against innocent men, women and children.
Gurmat does not promote such Ahimsa that results in making one a slave of the aggressor.
Gurmat does not promote such Ahimsa that empowers to aggressor to inflict atrocities on innocent people.
Siri Guru Gobind Singh jee in his famous Farsi shayer summed up Gurmat's stand on Ahimsa:
Chun kar az hameh heel-te dar guzasht.
Halal ast burdan b-shamsheer dast.
(When all means fail to (restore peace) it is justified (halal) to take Shamsheer (sword) in the hand (dast).
A Gursikh cannot not do anything if his or his Dharma's honour is taken. Sometimes, Shamsheer has to be taken in hand to restore peace. In such cases, according to Gurmat, this is what Ahimsa is.
Another distinction is that when a Gursikh fights in the battlefield, he does not do it under the influence of Krodh (anger) or (pride). A Gursikh lifts the sword, with Naam on his lips and Naam in his heart as well. If a Gursikh fighting his holy war, gets even an iota of anger or other vices, then his battle is no longer Dharam Yudh (holy war) but then he becomes liable for committing the sin of Himsa (violence).
A Gursikh has so much compassion and is so non-violent that he can't even pluck a flower for no reason (let alone hurting other jeevs) and when fighting the aggressor for the sake of Dharma, in an extreme case, a Gursikh becomes an embodiment of violence as Baba Banda Singh Bahadur in the battle of Sadhora, Samana and Sirhind, and Akali Phoola Singh in the battle of Nashaura.