Which regiment reinforced the Bastille attackers after 3 pm?

The regiment that reinforced the Bastille attackers after 3 pm was the Gardes Françaises, or French Guards.

The Gardes Françaises were a royal infantry regiment stationed in and around Paris. Many of its soldiers had become sympathetic to the revolutionary crowd, and some had mutinied or refused to carry out orders against it. Their military experience made them especially valuable to an otherwise improvised force of townspeople, artisans, and irregular fighters.

After fighting began at the Bastille, these mutinous French Guards joined the attackers after 3 pm. They brought organized firearms support and helped operate two cannons, intensifying pressure on Governor Bernard-René de Launay’s garrison. The Bastille eventually capitulated at about 5:30 pm.

The regiment is sometimes confused with the Swiss Guards, another royal unit associated with the revolutionary era. Swiss troops did reinforce the Bastille’s garrison, not the attackers. The Gardes Françaises, by contrast, were the royal soldiers whose defections helped the assault succeed.