The Czech Republic’s flag places a blue triangle at the hoist beside equal white-over-red horizontal bands.
The design began as the flag of Czechoslovakia. After the country became independent in 1918, it initially used the traditional white-and-red colours of Bohemia. That design closely resembled Poland’s flag, so a blue triangle was added at the hoist to create a more distinctive national symbol.
The National Assembly approved the design on March 30, 1920. Its designer was Jaroslav Kursa, an archivist in the Czechoslovak Ministry of the Interior. The flag was banned during the Nazi occupation, then restored in 1945. When Czechoslovakia dissolved in 1992, the Czech Republic retained the historic flag, while Slovakia adopted a different tricolour with its coat of arms.
The flag is often confused with Poland’s because both use white over red; the blue triangle is the crucial distinction. Slovenia and Slovakia also use white, blue, and red, but their flags are horizontal tricolours bearing coats of arms rather than this large hoist-side triangle.