In 2005, a planet capable of supporting life is discovered by scientists and named "Planet-G". NASA scientists send a signal but get no reply. Meanwhile, Alex Hopper is a talented but undisciplined slacker. His brother Stone, a naval officer in command of USS Sampson an Arleigh Burke, forces Hopper to join the Navy. A few years later, Hopper is a lieutenant in Combat Information Center on the USS John Paul Jones (DDG-53), an older sister-ship to his brother's command, the USS Sampson (DDG-102).Hopper also falls in love with Admiral Shane's daughter, Samantha, and wants to marry her, but is afraid of asking her father's permission, as he doesn't like Hopper. During the RIMPAC opening ceremony, Hopper gets into a brawl with Captain Nagata of the Japanese Maritime Self Defense Force, in charge of JDS Myoko (DDG-175). Hopper soon learns that he is to be kicked out of the Navy at the end of RIMPAC. Meanwhile, Samantha accompanies Army veteran and amputee Mick Canales on a hike on Oahu in order to help him adapt to his prosthetic legs.A small fleet of alien ships arrives in response to the NASA signal. One ship collides with an orbital satellite and crashes in Hong Kong, while five others land in the waters near Hawaii, hearing of this, the John Paul Jones, Sampson and Myoko are sent to investigate. The aliens erect a massive energy field around the islands, trapping all ships in the immediate area, and preventing any communication or assistance from outside the area protected by the field.The aliens attack, destroying both Myoko and Sampson, the latter with no survivors. Hopper's superiors are killed, leaving him in command of the John Paul Jones. Captain Nagata and some of his crew members are rescued from the waters and assists the Americans in setting up a discreet way to track the aliens using wave-detection buoys. During a night-time battle, the aliens and the Americans exchange pot shots, but Hopper manages to sink two alien ships. They rescue an alien from the water and discover the aliens are very sensitive to sun light and have to wear filters during the day. Using this knowledge, Hopper attacks another alien ship at dawn, using a sniper rifle with Nagata to breach their cockpit window and blind them with sunlight. Both ships are destroyed in the battle.Earlier, a group of alien footsoldiers and scientists lands on Oahu and attack the NASA communications array. Samantha and Mick narrowly avoid their detection, and run into a fleeing NASA scientist. Because the aliens' communications ship crashed in Hong Kong, the aliens plan to use the NASA array to signal their home planet to invade Earth. Realizing that a larger invasion might be imminent, Samantha manages to get a communications device and warns Hopper of the threat, initially, the Jones would destroy the array, but, with the destroyer sunk, they seemingly have no hope against stopping the aliens in time.Having no better options, the surviving crew of the John Paul Jones return to harbor and board the USS Missouri (BB-63), a 70-year old decommissioned battleship that has been converted into a museum, but armed with main battery of 16" naval rifles. With the aid of the museum ships caretakers, all elderly combat Navy veterans, Hopper manages to put the Missouri out to sea again. With some clever maneuvers, the Missouri destroys the last alien ship and shells the communications array, destroying the aliens and ending the threat of invasion.Back on shore, the crew and Mick all get medals, including a posthumous one to Stone, after the ceremony, Adm. Shane leads Hopper off to discuss his 'Terms of Surrender' over a meal.