The China-Europe railway network has evolved in the past decade from a nascent logistical experiment into a growing commercial alternative to maritime and air freight. In the wake of the US-Israel war on Iran, it might now be assuming an unanticipated role as a key security provider for transcontinental supply chains.

What began as sporadic trial runs has matured into a sprawling web of rail connections that currently links 235 cities across 26 European countries with more than 120 Chinese...