The national flag of Latvia was used by independent Latvia from 1918 until the country was occupied by the Soviet Union in 1940.
Its use of the flag of Latvia was suppressed during Soviet rule. After regaining its independence, Latvia re-adopted on February 27, 1990 the same red-white-red flag. Though officially adopted in 1922, the Latvian flag was in use as early as the 13th century. The red color is sometimes described as symbolizing the readiness of the Latvians to give the blood from their hearts for freedom and their willingness to defend their liberty. An alternative interpretation, according to one legend, is that a Latvian leader was wounded in battle, and the edge of the white sheet in which he was wrapped were stained by his blood. The white stripe may stand for the sheet that wrapped him. This story is similar to the legend of the origins of the flag of Austria.
The red-white-red Latvian flag was first mentioned in the chapters of Ditleb von Alnpeke’s Rhymed Chronicle of Livonia (Livländische Reimchronik). This historical evidence places the Latvian flag among the oldest flags in the world. The chronicle tells about a battle that took place around 1280, in which ancient Latvian tribes from Cēsis, a city in the northern part of Latvia, went to war, bearing a red flag with a white stripe. Wikipedia