Gulick's book is a perceptive discussion of the principles and use of the balance of power. Gulick starts by analyzing the assumptions, goals and means of the balance of power. Then he analyzed the Congress of Vienna which reset the balance of power after it was destroyed by the French revolution and Napoleon.

Gulick assumes the existence of a system of states of similar size, using permanent ambassadors to observe the states continuously, and a way of measuring the strength of a state. He explains that the balance of power is created to maintain the existence of the states system. Then Gulick defines the means to these aims. He mentions surveillance, alliances, coalitions, the ability to switch alliances quickly, and the determination to either destroy an enemy completely, or rebuild him to maintain the balance of power.

Napoleons military success destroyed the balance of power in Europe. Gulick describes the attempts to regain that balance. He begins with an alliance of Austria, Prussia and Russia to oppose Napoleon. Then Castlereagh arrived from Britain to create a grand coalition for several goals. The first goal was to defeat Napoleon, The second goal was to rearrange the borders, that Napoleon had changed, which would strengthen the balance of power. The last goal was to create a permanent diplomatic structure to maintain peace. Castlereagh encountered distrust among the allies, especially between Austria and Russia, which made his task difficult.

After the coalition achieved its first goal, to defeat Napoleon, they considered what to do with defeated France. The coalition wanted to maintain France as a power but not a danger. This would maintain the balance of power. Unfortunately the coalition to redraw the map of Europe to keep peace fell afoul of a disagreement concerning Saxony and Poland. When Napoleon returned, the allies rebuilt their coalition to defeat him, and continued to redraw the borders of Europe. Gulick concludes with a short discussion of the weaknesses of the balance of power, especially the problems of conflicting aims, and nationalism.

Gulick includes several primitive maps and a good bibliography. Since this is mainly a book about principles and their use, there is a minimum discussion about the individuals carrying out the principles. The nice thing about Gulick's book is that he supports his theory with excellent real life examples.