The Neptune anti-ship missile: The weapon that may have sunk the Russian flagship Moskva

Russia’s been having much harder time of its invasion of Ukraine than anyone — including the Russians — expected, thanks both to the scrappy resistance of Ukrainian fighters and the often surprisingly unsophisticated weapons they’ve been using, whether donated or bought from friendly countries or made in Ukraine itself.

It was a home-brewed Ukrainian weapon — two R-360 Neptune anti-ship missiles, to be specific — that may have earned the defenders arguably the most memorably victory of the war so far, the sinking of the Russians’ Black Sea flagship, the...