Historical experiences are a valuable source of knowledge about war and armed conflicts, therefore knowledge of history, including the causes of wars and methods of waging wars, are essential for politicians and commanders who live in times of war or the threat of its outbreak. The art of war has evolved over the centuries, but many of its basic principles have remained valid since the very beginning of warfare. Although every war is different, each has common features. Some elements of the art of war were named in the 20th and 21th centuries, but this does not mean that they did not find practical application in wars that took place in previous centuries. Historical experience has shown that numerous phenomena related to the conduct of war have repeatedly occurred. Concepts associated with war include: the window of opportunity, the Thucydides trap, hybrid warfare, indirect warfare, information policy, psychological warfare, security competition, and the balance of power. Knowledge of history allows us to more accurately predict how the political authorities of a given country may act and allows us to identify the signs and causes of wars.