Capital alerts: Delhi's long tryst with sirens, from World War II to today

Hindustan Times

12-05-2025

On Friday afternoon, a day before India and Pakistan called a ceasefire and halted military action, a wail-like sound rang through ITO, in the heart of Delhi. It was a long and metallic cry of an air raid siren atop the PWD building—part of a citywide revival of a wartime warning system. This was one of 500 sirens the Delhi government planned to install across the Capital, reintroducing a civil defence tool that once dictated everyday life during times of conflict.
For many, the siren brought back memories of wartime Delhi, when citizens lived in constant fear of air raids.
'I first heard the siren in 1962 when I was in college. The sirens were installed on campus, and the civil defence corps would visit to teach us safety drills,' said Sydney Rebeiro, 83, former dean of culture at Delhi University. 'They were sounded more frequently during the 1971 war with Pakistan. I remember once coming out of Regal Cinema and finding Connaught Place pitch-dark. Those days, the sound of the siren was unnerving, but the short burst that indicated the all-clear felt like music to the ears.'
'We got our information mainly from All India Radio, about various civil defence drills. We used to rush to cover windows with brown paper or newspapers, so light wouldn't filter out and, in case of a blast, the glass wouldn't shatter like shrapnel,' said Suresh Mehta, 70, a resident of Karol Bagh.
Air raid sirens: a history
Delhi's first air raid sirens were installed in the early 1940s by the British colonial administration as part of the Air Raid Precaution (ARP) programme during World War II.
With Japanese forces threatening British India's eastern front, Kolkata (then Calcutta) and Mumbai (then Bombay) were seen as vulnerable targets, and Delhi, being the seat of power, was also fortified. Sirens made by UK-based companies like Carter Nelson and Gent & Company were installed on government buildings and police stations across Connaught Place, Daryaganj, and Kashmere Gate, among other areas. These mechanical sirens produced sound levels between 100 and 120 decibels, making them audible within one to two kilometres under ideal conditions.
'Air raid sirens became prominent only after advancements in military aviation made it possible to target cities from the air,' said Amit Pathak, senior fellow at the Centre for Military History and Conflict Studies. 'From World War I (1914–1918) onward, cities began to face threats from zeppelins, biplanes, and later, long-range bombers. This changed the nature of warfare—civilians far from the front lines were now at risk. During World War II, cities became big targets and sirens were widely used in alerting civilians, especially as biplanes and bombers could strike with speed.'
London was the first city to use air raid sirens, beginning around 1915 during World War I, to warn residents of German zeppelin raids. These early warnings were sounded using hand-cranked or steam-powered devices that produced about 80 decibels of sound, audible over short distances—typically less than a kilometre—marking the advent of organised civil defence against aerial attacks.
Pathak said earlier wars were dominated by artillery, which had a more limited range and required a direct line of sight. 'Artillery battles were confined to the battlefield. Unless a city was under siege, there was little risk to civilians. As a result, there was no need for warning systems like sirens,' he said.
However, with the rise of air power, even cities hundreds of kilometres from the front could be bombed.
In India, the 1962 Sino-Indian War triggered a renewed push to expand the siren network in Delhi. As fears of Chinese air raids loomed, sirens were installed in newly developed government colonies, such as Netaji Nagar and Vinay Nagar (renamed Sarojini Nagar in the 1970s). About 30 sirens were installed during the war.
The Civil Defence Act of 1968 played an important role in strengthening India's preparedness during the 1971 Indo-Pak War, especially by formalising siren usage. The Act empowered authorities to install sirens on key buildings, and the civil defence corps carried out public awareness campaigns, blackout drills, and community training. Under its provisions, residents would douse lights, cover windows, and seek shelter when sirens rang.
'We took the sirens seriously. When one sounded, we stopped everything,' said Manohar Gupta, 79, who now lives in Janakpuri.
The return of sirens
But in the decades following the 1971 war, the siren system gradually fell into neglect. As direct armed conflicts almost ended and more sophisticated communication systems emerged, sirens were neither maintained nor upgraded. Most became defunct.
As the city reinstates a network of modern sirens in the wake of renewed Indo-Pak tensions following the Pahalgam terror attack, Delhi is once again turning to this old civil defence tool—now adapted to meet new urban complexities.
'These sirens are essential for public safety during emergencies. They will be centrally controlled by the National Disaster Management Authority (NDMA) and managed from a command centre. Once triggered, they will ring for five minutes, giving people time to seek shelter,' said Public Works Department (PWD) minister Parvesh Verma, during the ITO test.
Each of Delhi's 11 districts is set to receive around 10 sirens in the first phase. Fifty will be placed on prominent multi-storey buildings. Unlike old manually operated sirens, the new devices feature GSM-based remote activation, integrated into a software platform that allows all or selected sirens to be triggered simultaneously. HF radio backup and battery support ensure they work even during a mobile network failure or blackout.
However, the ITO test revealed some shortcomings. Although the sirens are designed to be heard up to 8 kilometres away, several people said the sound was too faint. 'People were more curious than scared. But the sound was faint—I could barely hear it,' a fruit-seller near the ITO junction said.
Officials have acknowledged the concern. 'We are reviewing the sound calibration,' a civil defence officer said. 'We're considering whether to increase decibel output or install more sirens closer together.'
Rebeiro said, 'The sociology of noise has changed. Delhi was quieter in 1971. Today, urban noise pollution is a big problem. It's no surprise that sirens don't carry far anymore.'
For younger Delhi residents, sirens are unfamiliar and unsettling.
'It felt like a dystopian movie. I didn't know whether to be scared or amused,' said 19-year-old student Aanya Gupta, who heard a siren during a civil defence drill on May 7. 'I hope they never have to be used for real in the city.'