The Ponziani is one of the oldest chess openings, first described by Luis Ramirez Lucena in 1497. It is sometimes also called the Staunton opening as Howard Staunton—the best chess player from 1843 to 1851—was a strong advocate for it. While still iconic, nowadays the opening is not considered to be quite as good as the Ruy Lopez or the Italian game.
The Ponziani opening starts with 1.e4 e5 2.Nf3 Nc6 3.c3.
C3 is used so d4 can be played later, while keeping a strong middle with the pawns. Black has three main options for counterattacks: the Jaenisch counter-attack, the Ponziani counter gambit, and playing d5. The only defense I will cover in this article (and the most common) is the Jaenisch, with nf6 attacking the undefended e4 pawn.
While it may look like the e4 pawn needs to be defended in this position, it is actually best to push d4 anyway, hanging the e4 pawn. Here black can either take your d4 pawn with their e5 pawn or take your e4 pawn with their knight. No matter what they take, push the other pawn which forces their knight to move.
In both variations, black is forced to move their knight; furthermore, in the kxe4 variation, if black’s knight moves to a5 then white can play pawn to b4 and trap the knight. Since the knights are forced to move in both variations, black’s pawn can be taken safely.
I’m not going to get deep into d5 by black, though Ponziani players should be ready for it. If black plays pawn to d5 against c3, then white has to play queen to a4: generally bringing out said queen so early is not a good idea; but, if necessary qa4 pins black’s knight and defends e4.