Colonel Nathan Hardy was an officer in the United States Air Force.
Colonel Nathan Hardy was a member of the team tasked with investigating the strange object in the Arctic Circle who greeted Lois Lane there when she arrived. He was later a witness of the ship flying away from the site.
Upon hearing General Zod's broadcast to the world, Hardy tracked down Lois to attempt to discover the whereabouts of the alien she encountered. When Superman handed himself into military custody, Hardy along with General Calvin Swanwick and Emil Hamilton spoke with Superman who told them that while he was not their enemy he feared that General Zod might be.
Superman handed himself over to General Zod's sub-commander, Faora, who also requests that Lois come along. Hardy objects, telling her that she isn't taking any Humans, only Superman. However, Lois volunteered to go regarless.
After Zod's forces started fighting with Superman in Smallville, Hardy lead the attack on them. Flying in a helicopter with a squad, it was brought down by one of the hostiles but Hardy survived. He was confronted by Faora who he opened fire on, but to no avail. Drawing his knife and prepared for the worse, he was saved by Superman who tackled her and occupied her focus, earning Hardy's trust in the process.
Afterwards, Lois went to Hardy with Jor-El's plan to get Superman's ship and use it against Zod's, he does so after knowing Superman was, indeed, on their side and after being given the ship, put it aboard a plane and flew it to Metropolis where Zod had unleashed his ship's gravity beam which was destroying the city. On their way to the ship, Faora jumped aboard and dispatched several men before throwing Lois out of the plane. Before she could get to Hardy, he piloted the plane directly into Black Zero with the phantom drive of Superman's ship exploding against Zod's causing a temporary portal to the Phantom Zone. Hardy quoted Faora from their previous encounter before Hardy and Hamilton were killed when the plane exploded on impact and Faora was sucked into the Phantom Zone.
Nathan Hardy was a iron-willed veteran of the US army. While somewhat gruff, Hardy is quite patriotically dedicated to his job and country. Hardy does, however, place national and global security above all else, being more than willing to join forces with Superman (an alien whom he initially mistrusted) and help the latter carry out an elaborate plan, as long as that meant defeating General Zod's invasion. After seeing Superman's extraordinary heroism in helping the US army fight off Faora and Nam-Ek, Hardy came to admire him, and insisted to his men that Superman was an ally. Hardy was also extremely brave, enough to pick a fight with the fearsome Faora several times.
- The codename "Guardian" is a reference to the DC Comics character Jim Harper/Guardian.