“If you tell a lie big enough and keep repeating it, people will eventually come to believe it.”
This technique of propaganda, used by Nazis during second world war and perfected by CIA afterwards, has been used enough times around the world and probably Hindus are its biggest victim. Since many years we are being told that “Sikhs Saved Hindus”. This statement has been repeated countless times by both Hindus and Sikhs and rarely has anyone tried to check its authenticity.
First serious attempt to demolish this myth was done by Indologist Koenraad Elst in his blog titled Guru Tegh Bahadur’s martyrdom 
Sikhism came into existence in late 15th century after birth of Guru Nanak in Punjab, but till early 17th century Sikhism was a non-military sect.
It was in time of Guru Hargobind who was the sixth Guru of Sikhs that Martial history of Sikhism begins. Guru Hargobind was friend of Jahangir. Mohsin Fani who was the companion of Guru Hargobind and author of The Dabistan writes ““Hargobind never separated himself from the stirrup of victorious Jahangir.” It was probably because of this friendship Jahangir invested Guru with some supervisory power over affairs of Punjab and he got command of Mughal contingent of 700 horses and 1000 foot and 7 Guns.
 In this book called The Dabistan one more incident is mentioned which is worth mentioning. This incident is related to Goddess Naina Devi. Guru visited Kiratpur which is not far from Naina Devi. Here one of the Guru’s disciple named Bhairo went to temple and broke nose of goddess’s idol , neighbouring hill Raja complained about this to Guru He summoned Bhairo who denied the charge. The servants of the Rajas asserted that they recognised him. Bhairo replied: “O Rajas! ask the goddess. If I am named, you may kill me. “The Rajas said: “O fool! how can the goddess speak?” Bhairo laughed and said: “Have you discovered who is a fool? If your goddess cannot stop breaking its own head, nor does she name the culprit, what good can you expect from her worship?”
The Rajas kept quiet, and most of the people of the area became Guru’s disciples.  Rather being savior of Hindus in early part after their militarisation Sikhs were allied with Mughals and also did some Anti-Hindu acts. These acts probably served as an example for Sikh extremists in 1980s when they attacked temples. Guru Hargobind was succeeded by Guru Har Rai in 1644 as the seventh Guru who remained Guru till 1661.
After Guru Har Rai there was dispute about succession of Guruship between Ram Rai and Guru Har Krishan so Aurangzeb summoned Guru to Delhi, but mother of Guru was terribly afraid of Aurangzeb So Mirza Raja Jai Singh of Jaipur sent his troops to Kiratpur to escort him to Delhi and gave his personal assurance for Guru’s Security.   So as we saw rather than Sikhs saving Hindus it was a Hindu King who provided security to Sikh Guru.
Guru Har Krishan died in Delhi in 1664 he was succeeded by Guru Tegh Bahadur. After becoming Guru he undertook a tour of Malwa and journeyed from village to village preaching his gospel. Aurangzeb could not tolerate Guru Tegh Bahadur’s preaching so he ordered his arrest and imprisoned him in Delhi. Emperor issued orders of Guru’s execution but Prince Ram Singh Son of Mirza Raja Jai Singh took full responsibility of Guru’s conduct and got him released. 
Guru Tegh Bahadur was executed in 1675 on orders of Aurangzeb after which he was succeeded by Guru Gobind Singh who had already formed Khalsa in 1699. Guru Gobind Singh had many skirmishes against mughals; because of it Wazir Khan started hating Guru and when he captured two younger sons of Guru he executed them and threw away their bodies. A local Baniya named Todar Mal, picked up the bodies and took them to the Guru’s mother who collapsed at first sight and died. Todar Mal cremated the three bodies. 
After death of Guru Gobind Singh it was Banda who led the Sikh army by next few years he was also executed by Mughals in 1716.
Before that one important incident had happened which deserves our mention, Mata Sundri and Mata Sahib Devi widows of Guru Gobind Singh were living in Delhi. Mata Sundri had adopted a boy and named him Ajit Singh. Soon after their house was sacked and boy was killed, they had to flee to Mathura where Sawai Jai Singh of Jaipur provided them with a suitable residence and a handsome allowance for their subsistence. 
Maratha Campaigns in North India, Nadir Shah’s Invasion and then Abdali’s invasions weakened the Mughal Empire and gave chance to Sikhs to increase their power. They organized themselves in Misls and fought many battles against Afghans but these Misls weren’t very powerful so main contest for control of Punjab happened between Afghans and Marathas. Afghans were able to defeat Marathas at Panipat in 1761 but Marathas regained their influence in North under leadership of Mahadji Scindia who ruled from Gwalior and Mughal Emperor in Delhi was his puppet. Mahadji had greater influence even in Punjab and Sikh chieftains paid tribute to him. 
Sikh Misls sustained themselves by plundering and terrorising people living in Punjab and neighboring region. They used to plunder everything that came their way, one of the worst example of their plunder was Massacre in Kumbh Mela of 1796 when hundreds of pilgrims were masscared by Sikhs led by Sahib Singh. 
Ranjit Singh annexed most of the Chieftaincy of these small Sikh Chiefs and formed a Kingdom of considerable size which was spread from Sutlej in the East to Peshawar in the west. Hindus had great influence during this period In fact many crucial battles for Ranjit Singh was won by Hindu Generals. Battle of Attock fought against Afghans in 1813 It was first Significant victory of Sikhs over Afghans. Sikh army in this battle was led by Diwan Mokham Chand. Siege of Multan(1818), Conquest of Kashmir(1819) were some other crucial wars against Afghans it was Misar Diwan Chand who led Sikh to victories in these battles. 
Ranjit Singh died in 1839 and since then disintegration of his state began. There was constant power struggle between various power centres. Hira Singh tried his best to keep Sikh state intact but he was assisinated. That served as last nail in coffin of Sikh Kingdom which soon got conquered by Britishers like many other kingdoms in India. 
In the end it can be colncluded that Sikhs aren’t the sword-arm of Hinduism. There are many incidents in History of Hindus protecting Sikhs and there are some incidents of Anti-Hindu activities by Sikhs. By complimenting Sikhs with exaggerated version of their history will not benefit Hindus but it will surely give rise to the people like Yograj Singh who will not leave any chance to humiliate Hindus.
 History of Sikhs Vol-I The Sikh Gurus Page 163
 History of Sikhs Vol-I The Sikh Gurus Page 172
 History of Sikhs Vol-I The Sikh Gurus Page 181-82
 History of Sikhs Vol-IV Sikh Domination of the Mughal Empire Page 331
 History of Sikhs Vol-I The Sikh Gurus Page 195
 History of Sikhs Vol-I The Sikh Gurus Page 299
 History of Sikhs Vol-IV Sikh Domination of the Mughal Empire Page 332-33
 New History of The Marathas Vol-III Page 273
 History of Sikhs Vol-IV Sikh Domination of the Mughal Empire Page 280-86
 History of Sikhs Vol-V The Sikh Lion of Lahore Page 100-102, 109-112, 128-130
 History of Sikhs Vol-2 1839-1964 Page 28-35