Republic of Chad
Who & why: Chad adopts its national flag on 6 November 1959 as an autonomous republic within the French Community, and becomes fully independent on 11 August 1960 under President François Tombalbaye. Tombalbaye's increasingly authoritarian rule provokes a northern rebellion by 1965–66, opening a civil-conflict era that runs through his 1975 overthrow and assassination, a fractured mid-1970s–80s civil war, direct Libyan military intervention and occupation of the northern Aouzou Strip through the 1970s and 80s (finally resolved by a 1994 International Court of Justice ruling in Chad's favor), Hissène Habré's harsh 1982–90 rule, and Idriss Déby's three decades in power from 1990 until his 2021 death at the front against rebels, succeeded by his son. State factually: the flag itself is untouched by any of it.
What it represents: a simple vertical tricolor combining pan-African green-yellow-red sentiment (swapping green for blue) with the format of the French Tricolor — blue for sky, hope, and unity, yellow for the sun and the Sahara, red for the blood of independence and unity.