Sphyrna-class corvette

"Those are our reinforcements? Some old transports?''" "''In our position, you take what you can get, kid."

- Ezra Bridger and Kanan Jarrus

Hammerhead corvettes, were a model of corvette that saw wide use in the period leading up to, during the Galactic Civil War and during the cold war, where they would be fielded by a rebel cell as well as the Alliance to Restore the Republic and the Resistance.

Characteristics
Sphyrna-class corvettes were inspired by a starship design that dated back centuries prior to the Imperial Era that was designed by Corellian Engineering Corporation. Throughout its existence, at least two different variants of the Hammerhead corvette existed. The one most commonly seen utilized by rebel cells as well as by their successor, the Alliance to Restore the Republic, featured its characteristic vertically-elongated bridge, a large ventral cargo bay and three dual laser cannons.

By 0 BBY, the Alliance had either modified its previous Hammerheads or had begun utilizing a slightly different model. This Hammerhead was structurally the same, although it featured several new additions. These included two extra modules mounted to the port and starboard of the craft, six escape pods in place of the cargo bay, and a fourth sublight drive mounted on top of the primary three, giving it enough power to single-handedly move a disabled Star Destroyer. This was the version used the most during the Battle of Scarif.

Early rebellion
After learning of the rebels losses at the battle on Garel, Imperial senator Bail Organa of Alderaan dispatched his adopted daughter, Princess Leia Organa, along with three Hammerhead corvettes&mdash;P1, P2 and P3&mdash;to Lothal to expand the rebel fleet, under the guise of delivering relief supplies to the people of Lothal. The princess planned for the rebels to steal them to conceal Alderaan's involvement with the rebellion, but Lieutenant Yogar Lyste installed gravity locks to prevent the corvettes from taking off. With the help of former Lothal governor Ryder Azadi, who had constructed the locks while he was in prison, the rebels were able to commandeer the corvettes and add them to their growing fleet.

In 2 BBY, the former Sith Lord Maul assaulted one of the rebellion's corvettes. He interrogated the crew, leading to Maul capturing the Ghost personnel in order to unlock holocrons.

Later, Phoenix Cell escorted one of their transports to evacuate rebel sympathizers at Mykapo in front of an imminent Imperial takeover. The same transport, the red-painted P2, was later destroyed during the Battle of Atollon.

Galactic Civil War
"Call up a Hammerhead corvette. I have an idea."

- Admiral Raddus during the Battle of Scarif

After the rebellion was reorganized into the Alliance to Restore the Republic, several modified Hammerheads partially made up the motley assortment of vessels that was the nascent Alliance Fleet. One such ship was the Lightmaker, which was a part in Admiral Raddus' fleet just prior to the Battle of Yavin, under the command of Kado Oquoné. The vessel was present at the Battle of Scarif. During the battle, Raddus ordered it to ram into the side of the disabled Imperial I-class Star Destroyer Persecutor, causing it to crash into a second Star Destroyer, the Intimidator, and then into the Shield Gate, allowing the Death Star plans to be transmitted from the Imperial base on the planet's surface. After the transmission is received by the fleet, at least one Hammerhead corvette, along with some of the fleet began the jump into hyperspace just before the arrival of the Devastator.

At least one Hammerhead was still in the Alliance Fleet shortly after the siege on Tureen VII.

Cold war
One Hammerhead was part of the Resistance navy. The Sterdic Star was used during the mission to Taul.

Behind the scenes
Hammerhead-class corvettes first appeared in "A Princess on Lothal," the tenth episode of the second season of Star Wars Rebels, which also saw the introduction of Princess Leia Organa on the show. The ships are based on the Hammerhead-class cruisers from the now Legends video game Star Wars: Knights of the Old Republic.

Non-canon appearances

 * LEGO Star Wars: The Force Awakens