理論上，所有國家，無論大小，必然具有地方層次的思考，國家在對外政策上有其戰略假設，這些戰略假設就構成地緣政治密碼，日本也不例外。豪斯霍佛「泛區」與「生存空間」的概念，在日俄戰爭之後，日本於1930年代將其轉化為「大東亞共榮圈」。地緣政治密碼是關於一國之國家利益的定義、對這些國家利益之外部威脅的標定、一組針對這些外部威脅的計畫性回應方案，以及關於這些回應方案的「正當化」論述。當一國追求在其周邊區域更具影響力，並成為區域強權時，則是以地區層次制定其外交政策；少數在國際政治深具影響力的國家，則從全球地緣政治視角制定外交政策。大東亞共榮圈基本上是日本據以美化帝國主義殖民的代名詞，藉以降低亞洲國家的抵抗感，以號召亞洲國家協助其太平洋戰爭。而大東亞共榮圈的實質內容並非互惠互利的區域整合，而是一個以日本為主導的附庸國系統。從國際政治的權力賽局來看，背後寓意著地緣政治的論理。本文旨在運用地緣政治研究途徑，理解日本的地緣政治，進而解析日清戰後的東亞地緣政治板塊運動與19世紀東亞地緣戰略意涵，以及大東亞共榮圈論理中所醞含的地緣政治密碼。

Theoretically, all countries would project their foreign adversaries which might be threats to their national security interest. These strategic assumptions in the foreign policies are based on the geopolitical code. Japan is no exception.After the Russo-Japanese War in year, the concept of "Pan-ideen" and "Lebensraum" from Karl Haushofer, had transformed and developed into "Greater East Asia Co-prosperity Sphere" in 1930.The geopolitical code is the multiple considerations) of national interest, demarcation of exterior threat and a set of projection to respond exterior threat as well as to justify about these responses or operations. When a country exercise its influence in peripheral region and become a regional power it would upgrade its foreign policy from regional level to a wider consideration of global level.Basically, Greater East Asia Co-prosperity Sphere is a pseudo term of Japanese imperialism colonizes. It was created to reduce the Asian country's resistance and to call for Asian countries to assist its Pacific War.The contents of Greater East Asia Co-prosperity Sphere are by no means targeted for mutually beneficial interaction region conformity, in fact it was aimed to place Japan at the core of East Asia. In term of international politics, it has the implication of geopolitics.By geopolitics approach, this article is trying to understand Japan's geopolitics, to analysis geopolitical changing and the geo-strategy of East Asia and the geopolitical code of geopolitical code in 19th century.