To plug the gaps in air defences exposed on both sides in the 2019 conflict, India secured Russia's battle-tested S-400, a mobile anti-aircraft missile system. Pakistan obtained the HQ-9 from China, which is based on Russia’s S-300, one notch down.

For 10 nights straight, gunfire between Indian and Pakistani soldiers has echoed from the mountains and deep valleys that form the heavily defended de facto border between the nuclear-armed rivals.