Does chicory make coffee stronger?

We assume by ‘strong’ you mean more caffeine. Then the answer is NO. Chicory does not have any caffeine in it. As far as taste is concerned, it does impart a distinct taste to the final brewed cup, which is not too different from pure coffee but it can be easily told apart.

Chicory was added to coffee primarily due to its lower cost and due to scarcity of coffee during the war years.

Chicory plant is native to France. Some cultures around the world still love that taste. Kentucky in USA and South of India are two examples where it is routinely added to brewed coffee.