An urumi (Malayalam: uṟumi; Sinhalese: ethunu kaduwa; Hindi: āra) is a sword with a flexible, whip-like blade, originating in modern-day Kerala in the Indian subcontinent. It is thought to have existed from as early as the Sangam period. [~600BC-300AD]
The urumi is handled like a flail but requires less strength since the blade combined with centrifugal force is sufficient to inflict injury. As with other “soft” weapons, urumi wielders learn to follow and control the momentum of the blade with each swing, thus techniques include spins and agile manoeuvres.
These long-reaching spins make the weapon particularly well suited to fighting against multiple opponents. When not in use, the urumi is worn coiled around the waist like a belt, with the handle at the wearer’s side like a conventional sword.
I mean, if a military were to have the financial means to offer a cannon to every soldier, they would. Economics are the backend of every war. In 600 BC, a flexible sword would be both far more expensive and less effective than a spear, which is the crux of my question. I only read the wiki after my comment so I take back halberds. 7355608 proposed an interesting use case in a casual carry belt that feels reasonable.