India, May 12 -- 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 saf...