system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why were the mongols so successful?
gpt
Because they have excellent military tactics. 

The Mongols had vast vanguard units, so they could go ahead of the main troops and spy on what lies ahead. these fast, mobile units were also extremely deceiving to enemies who were often lured by their low numbers and pursued to hunt them, only to be surrounded and trapped by the major troops ahead. the Mongols had excellent logistics to allow communication, supplies, and movement across extremely long distances. they used frozen rivers as the communication lines and were able to travel 50 miles in one day.

During a battle, they usually elected elevated hills to be the main communication points and used flags as the way to communicate with the troops. the troops were grouped into 10, 100, 1000 and 10,000, where each unit had a competent leader. the invasions were carried by armies approaching the enemy from numerous sides. the conquest of Hungary was done with multiple points to overwhelm the enemy. they pushed along the Danube from Moldavia, across the Carpathian Mountains from Poland, and Czech lowlands to be met in the center of Hungary. the sheer size of the army was enough to destroy any opponent.

the Mongolian expansion was based on the blitzkrieg tactic, and was not intended to acquire territory the way it was done by European, Roman, Greece, Persian, or Arabian empires. these empires wanted to create material wealth from taxes imposed on the population, which meant very little to Mongols. the acquisition of the territory meant thorough destruction of land, destroying any possible landmarks, killing entire populations, and even damaging the habitable environment. the environmental damage in Central Asia is still visible to this day. another effective Mongol tactic was to kill all the ruling elite, as was done in Baghdad.

TLDR; They mastered the real time strategy game in terms of scouting, resource management, unit micro and communication better than everyone else at the time.