Well, he might use his powerful jutsu like the Rasengan. He could also summon his toads to help him out in the battle against the army. Maybe he uses his shadow clone technique to confuse the enemy and then strike them when they're vulnerable.
Well, he might start by using his charisma. Naruto has always been good at making friends. He could reach out to old allies from his village, like Shikamaru and Choji. Also, he might convince some of the outcast ninja who have been mistreated in other villages to join him. His reputation as a hero who saved the world would surely attract a lot of people.
Perhaps it's for exploration. Naruto is always curious about the world outside. The robots can be sent to explore dangerous or uncharted areas where it might be too risky for humans to go. They can collect information and report back to Naruto.
Maybe Naruto has some knowledge from an unexpected source. For example, he could have met a wandering inventor who taught him the basics of robotics. With his determination and quick learning ability, he then starts building the robot army. He might also use his chakra in some unique way to power or control the robots.
Well, Naruto himself would probably be really excited. He'd be running around the military base, trying to make friends with everyone. His positive attitude might initially seem out of place in the strict military environment but could also start to change the atmosphere, making it more lively.
Well, obviously Naruto's friends like Sasuke, Sakura, and Shikamaru could be part of the army. Sasuke with his powerful Sharingan and combat skills, Sakura with her medical ninjutsu and newfound strength, and Shikamaru with his strategic mind. Also, ninja from other villages like Gaara from the Sand Village, who has his own unique abilities and a bond with Naruto, would likely be in the army.
I'm not sure specifically as there could be many different plots in a 'Naruto Army of One' fanfiction. It might involve a character, perhaps Naruto himself, facing challenges alone against a large force, like an army, and having to rely on his unique skills and growth throughout the Naruto universe.
Well, one idea could be that Naruto is somehow transported to ancient Egypt and gets involved with the Jackal Army. Maybe he uses his ninja skills to help them in a battle against an evil force that threatens both the ninja world and the Egyptian realm.
It might be a fanfiction that focuses on two individuals in the Naruto series who come together to create an army. This could involve characters from different ninja villages uniting under their leadership. They could be facing a great threat that requires them to gather forces and use their combined skills, which are often unique to the Naruto universe like jutsus and strategic ninja thinking.