Roman Republic:

The heavy infantry of the maniples were supported by a number of light infantry and cavalry troops, typically 300 horsemen per manipular legion. The cavalry was drawn primarily from the richest class of equestrians. There was an additional class of troops who followed the army without specific martial roles and were deployed to the rear of the third line. Their role in accompanying the army was primarily to supply any vacancies that might occur in the maniples. The light infantry consisted of 1,200 unarmoured skirmishing troops drawn from the youngest and lower social classes. They were armed with a sword and a small shield, as well as several light javelins.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What type of infantry joined light, and the cavalry in battle?
heavy infantry