Kingdom of Belgium
Who & why: Brussels is liberated on 3 September 1944; the government returns from exile in London and the monarchy is restored, though King Leopold III's controversial 1940 surrender triggers a bitter postwar "Royal Question," resolved only by his 1951 abdication in favor of his son Baudouin. Belgium becomes a founding member of NATO (1949) and the European project that follows, with Brussels emerging as its de facto capital.
What it represents: the same 1830 tricolor, unchanged, now the longest-continuous flag these provinces have flown — the 1970–1993 constitutional reforms that turn Belgium into a federal state of Flemish, Walloon, and Brussels regions happen entirely underneath this one national flag, which none of that devolution ever touches.
Both sources date the current flag to 1831, before this era begins in 1944, so the flag was already in use at the start. Wikipedia's infobox gives the adoption as 23 January 1831; Flags of the World dates it 23 January 1831.
- Flag of Belgium — Wikipedia compiled
- Belgium — Flags of the World (CRW Flags) compiled
Not established: Only the year the current flag was adopted was compared; the design and the swatch colours were not checked against a specification.