What was one of the most remarkable achievement of the indus valley people?

One of the most remarkable achievement for the Indus Valley people were Harappa and city of Mohenjo-Daro they were known for organization and for their layout too. They had plumbing and drainage system, as well as indoor toilets.

answer; the period of time known as the middle ages;

united states reinforcements contributed greatly to three allied victories in france at: cantigny (first major american battle), argonne (the largest in the united states military history, involving 1.2 million american soldiers), and château-thierry (one of the first actions under general pershing).