There is no divine right of Kings or Republics. There is no natural form of government: societies organize themselves in the means most efficient to their needs and values. Leaders of society naturally arise through inherited intergenerational wealth, of financial, scientific, technical, political and industrial nature. This is mistaken for nobility. Leaders of society naturally arise through honor and reliability, through valor and courage, through reliance on experienced advisors, through personal experience, through honesty, through a cooperative and collaborative nature, through gratefulness and courtesy, through ambition, through enthusiasm, by avoiding procrastination, through self-control, through resolution, through well-skilled servants, through discipline. People will naturally give fealty to such a leader possessed of these qualities.
And when there is but one such leader, an autocrat is seen to arise. When there are a few such leaders, monarchy is seen to arises. When there are more such leaders, a republic arises. When there are many such leaders, a democracy arises.
To dominate or conquer your enemy it is necessary to become their leader; understand not only who their leaders are, but the source of their leadership; become a better leader.
The means of becoming a better leader are simple. To improve your intellect, develop curiosity, inquiry, learning, perception, memory, mental reflection before and after action, deliberation in taking action, logic (especially inference), and decisiveness. Valor, determination, purposefulness, quickness, and probity will all improve enthusiasm. Develop self-control through training, self-improvement, foresight, opportunism, good humor, leniency and mercy, freeing yourself from emotionality, smiling, and maintaining the customs of the elderly.
A well endowed land will produce a leader, or if there is democracy there, a rich people. A well endowed leader is, similarly, an asset to their people. As the highest use of wealth in the treasury is to withstand calamities of long duration, so too is the highest use of the leader to protect their people from fickle luck. Many misfortunes are apt to occur, even in a well-endowed land: war not least of them. Always be prepared for this, and all other emergencies. Not every emergency can be foreseen or prepared for, and sometimes strength and readiness are insufficient - but no leader ever failed for having become too strong, too ready.
A leader who is unprepared and unready, one who is of poor character, unintelligent, or otherwise has become their own enemy is easily uprooted. A leader who may be made to become their own worst enemy is soon destroyed. But a leader who is their own friend will persist, for persistence is part of their nature. Even if one good leader possesses only a small Kingdom, that leader will conquer the world with their leadership, and will never ever be defeated or conquered.