Bangladesh, Oct. 4 -- The war in Ukraine, now well into its third year, has become more than a bloody geopolitical struggle between Moscow and Kiev. It has also turned into what many analysts describe as a vast testing ground for Western arms manufacturers, a place where new weapons technologies are deployed, refined, and marketed in real time. For Europes defense startups, the conflict has unleashed what the New York Times recently called a “gold rush” in weapons investment, as venture capitalists and governments alike pour billions into a sector once regarded as unattractive for private money.

This rapid influx of capital into European military tech firms underscores how deeply the war has reshaped the economic and strategi...