This is a tale of the enlargement soft power which helped transforming relation between countries in the triangle Zagreb – Belgrade – Sarajevo. At the territory of this triangle, there are approximately fifteen million people of different ethnic and religious backgrounds who have been deeply divided throughout the history over the issue of past and who can hardly agree on the contents of a history textbook, but who are nonetheless very similar and economically and culturally mutually interdependent. Observing this triangle as a geometric shape, the lines Zagreb – Sarajevo and Sarajevo – Belgrade are catheti, while the line Belgrade – Zagreb represents a hypotenuse of this triangle. If for a moment we convert the relations between the states into a geometric form, by using the Pythagoras’ Theorem we could conclude, of course symbolically, sums of (squares) of relations of Sarajevo with other two capitals is equal to the (square) of the relation between ZAGREB and BELGRADE, as its hypotenuse. This geometry lesson and its perhaps forced application on the regional relations leads to a unique conclusion which very much fits the reality: Zagreb and Belgrade always held and still hold the key to regional relations, particularly at the territory that is the subject of this analysis.