Irrigation was a contribution made by the mayans egyptians babylonians

Egyptians

Explanation:

From the earliest times we find ourselves in a very well organized "irrigation department", equivalent to a Ministry, whose bosses were always the most famous architects of Egypt. Often in the documentation, it is among the titles of the highest dignitaries, that of "the chief of irrigation", One of the main kites of this department was to monitor the flood and the decrease in the level of the Nile waters. For this, wells that communicate with the river are excavated and in any place that is placed on a stick or scale that indicates the highest level of water in each year.

he sent troops to protect the students as they entered the school.