English: This map depicts the world as divided by geostrategist Alfred Thayer Mahan in his 1900 piece The Problem of Asia.

Asia is divided along the 30 north and 40 north parallels, represented here by green lines.

Colored in red are the two allied land powers, the Russian Empire and France. In lighter red are the portions of Asia above the 40th parallel under effective influence of Russian land power.

Colored in blue are the four allied sea powers, Great Britain, the German Empire, Japan, and the United States. In lighter blue are the portions of Asia below the 30th parallel subject to effective control by sea power.

In between the 30th and 40th parallel is what Mahan termed the "Debatable and debated ground," subject to competition between the land powers and sea powers.

Circled in green are key isthmuses identified by Mahan: the Suez Canal, Panama Canal, Turkish Straits, Strait of Gibraltar, and Danish Straits.

Source

Created by myself, user:Perceval, using the :Image:BlankMap-World-WWI.PNG.