PALO ALTO, Calif. - Sitting in a wheelchair in his dark blue dress uniform, Marine Lance Cpl. Angel Gomez lifted his left hand and swore allegiance to the United States on Thursday, becoming a citizen of the country he had already fought so hard to defend. Gomez, 19, had been practicing for weeks in hopes of raising his right hand during the oath, but his injuries proved too grave. A brain injury he suffered during a bomb explosion in Baghdad three months ago has left him partially paralyzed, and he struggles to speak. Gomez, who grew up in a Mexican village in the state of Jalisco, became a legal U.S. resident 12 years ago when his family moved to Farmersville, Calif., to join his father, a U.S. citizen. He enlisted at 17 against his mother's wishes, saying he wanted to serve in the bravest branch of the U.S. Armed Forces. He completed his training to drive a Humvee at Camp Pendleton, near San Diego, in February, and was deployed to Baghdad with the Marine Corps a month later. Within weeks, a bomb exploded near his vehicle. Shrapnel damaged the part of his brain that governs speech and motor skills. Now his head is encased inside a plastic helmet, and he can say only a few words at a time. His eyes shone as he responded to questions about how he felt becoming a citizen. "Fine. That's it," said Gomez, fingering a button on his uniform, a Purple Heart pinned to his chest. As one of about 31,000 non-citizens serving in the U.S. military, Gomez became eligible to apply immediately for citizenship under an executive order signed by President Bush after Sept. 11, 2001. This year alone, more than 4,000 members of the U.S. Armed Forces have been naturalized, at military bases and embassies overseas, and in quiet ceremonies like this one, in the traumatic brain injury unit of the Palo Alto veterans hospital. "In the Marines he was fighting for the country and the ideals he believed in even though he wasn't a citizen," said 1st Lt. Nathan Braden, a spokesman for Camp Pendleton. "That is definitely something that's commendable." Gomez has recovered remarkably under therapy, said his occupational therapist Daniela Lita, but he still faces months or years of rehabilitation to relearn how to walk, shave and express himself. His parents have followed him from hospital to hospital, crisscrossing the country to stay with their son. Each night, Gomez's father takes him to the hospital parking lot to sit in the car and listen to songs he knew as a child - tunes with big-band orchestras from Jalisco, with lyrics about boas and dancing. Gomez said he remembers the songs, but he can't sing them. "I told him not to go and fight. I'm sad that he's come back like this," his mother, Antonia Gomez, said in Spanish. "Now we talk to him about things he did when he was little, to distract him." Thursday, at least, was a good day. Holding his certificate of citizenship with his parents behind him, Cpl. Gomez raised his head. Asked how he felt, he offered one word: "Joy."