Laos–Vietnam border

[1] The border starts in the north at the tripoint with China and proceeds overland in a south-eastwards direction.

[2] From the 1860s France began establishing a presence in the region, initially in modern Cambodia and Vietnam, and the colony of French Indochina was created in 1887.

[2][3] Laos was at this point part of the Kingdom of Siam (the old name for Thailand), however it was annexed to French Indochina in 1893 following the Franco-Siamese crisis.

[2][4][3] The precise date of the delimitation of the frontier is unclear; the International Boundary Study states that "The juridical basis of the Laos–Viet-Nam boundary probably stems from ancient treaties and custom as modified or made more specific by decrees of the Indochinese administration.

[2] During the Vietnam War the border was crossed by Viet Cong supply lines, most notably the Ho Chi Minh Trail, causing it to be heavily bombed by American forces.