How can you explain the high combat capability of the Mongolian army?

The Mongols occupied marginal steppes and this determined the occupation of the nomadic people. The constant struggle for better pastures made Mongolian men good warriors. From the age of three, the boys began to teach the art of war, to raise real warriors who could only win. Subsequently, they will become a threat to many peoples and the military successes of the Mongolian army will allow them to expand their state from the Far Eastern steppes to the cities of Europe. The fighting efficiency of the Mongolian army was facilitated by objective reasons:
1. The number of conquered tribes whose warriors formed the backbone of the army.
2. Brutal discipline.
3. Constant training as close as possible to military operations.
4. Talan of military leaders who were appointed only for personal qualities.
5. The presence of the newest weapons of the time.