They were an elite squad that provided protection in the Indian capital - until now.
The large black-faced langur monkeys have been on guard for decades to keep out armies of smaller rhesus monkeys that plague Delhi, protecting events like the 2010 Commonwealth Games and visiting foreign dignitaries, and keeping order in the hallowed halls of parliament.
But a move by the New Delhi government will see the langurs eased out from such duties after protests by environmentalists.
Tens of thousands of rhesus monkeys have swarmed over urban India.
In densely populated areas the wild monkeys occasionally have run-ins with humans when they look to steal or snatch food.
Cases abound in New Delhi of the monkeys attacking people when they are confronted.
As culling of the animals is resisted by devout Hindus - who revere them as incarnations of the monkey god Hanuman - and animal activists, langurs were deployed to scare them away.
Under country's Wildlife Protection Act, 1972, the langurs are a protected species and cannot be owned, sold or hired out.
Any violation of the law entails a three-year jail term. Yet New Delhi's civic authorities and several government offices hired the services of the trained langurs to keep their premises free from the invading rhesus monkeys.
The handlers who usually own the langurs carry their animals in chains. But this came under fire recently, after animal rights activist and opposition party Bharatiya Janata Party leader Maneka Gandhi began protesting about the chaining of the animals. India's Ministry of Environment and Forests issued letters to New Delhi state and federal ministries alerting them that chaining of the langurs and putting them to work was illegal.
Last month New Delhi's urban development ministry issued a notice asking civic agencies to stop using langur guards.
Mohammad Aftab, a langur handler who earns around 8,000 rupees (HK$1,150) a month, said: "For eleven years I guarded a government office complex using my langur and the authorities were happy with its service.
"But from the beginning of this month I have been thrown out of a job. The office informed us last week that it would not be able to renew my contract."
But the rhesus monkey population in New Delhi is growing and, with that, the menace they cause, said an office worker.
"The pestering [rhesus] monkeys vanish from our office buildings as soon as the trained langurs appear on the scene. The langurs are very smart in their job," said Sunita Singh, an agriculture ministry clerk. "But we heard that from next month the langur guards will not be on duty around our office any more. I am sure the rhesus monkeys will return to wreak havoc."