Naruto would face the psychological challenge of fighting alone. He is used to having his friends by his side. Without their support, he might have moments of self - doubt. The army might also use psychological warfare against him. They could taunt him or try to make him angry to disrupt his focus. In terms of actual combat, the coordination within the army could be a big obstacle. If they are well - organized and work together effectively, they could set up complex traps and ambushes for Naruto. And if the army has access to some sort of large - scale destruction jutsu, Naruto would have to find a way to either avoid it or counter it.
Well, Naruto has a lot of powerful jutsus at his disposal. His Rasengan alone can cause a great deal of damage. He could also use his shadow clones to create distractions and attack from multiple angles. And let's not forget his Nine - Tails chakra. With that, he could boost his strength and speed to take on a large number of enemies at once.
If Naruto were to fight an army in fanfiction, he would bring his unique skills to the battle. Naruto is known for his never - give - up attitude. So, even if the army seems large and intimidating, he would keep fighting. He could use his Uzumaki bloodline abilities, like his strong life force and large chakra reserves. Also, his ability to make friends and allies might come into play. Maybe he would convince some members of the army to switch sides. His transformation into different forms, such as the Six Paths Sage Mode, would give him an edge in combat. With his speed, he could quickly move around the battlefield and take out key targets in the army.
His friends from the Hidden Leaf Village might help. For example, Sasuke could be a powerful ally. He has his Sharingan and his own set of powerful jutsu.
One of the most exciting scenes could be when Naruto first unleashes his Nine - Tails chakra in a full - blown rage. The red chakra would surround him, his eyes would turn into slits, and he would let out a powerful roar. As he charges into the army, the soldiers would be both terrified and in awe of his power.
In a Naruto fanfiction where he fights an army alone, he could win through his vast array of jutsu. His Shadow Clone Jutsu could be used to create multiple decoys, confusing the enemy. Also, his Rasengan, a powerful and concentrated chakra attack, could take out many foes at once. His Nine - Tails chakra might also give him a huge boost in power and endurance, allowing him to keep fighting against overwhelming odds.
Sakura could be a leader. She has strong medical ninjutsu skills and is also a very capable fighter. She could lead the medical unit in Naruto's army, taking care of the injured and also providing strategic advice based on her intelligence. Another possibility is Shikamaru. He is known for his brilliant strategic mind. He could be in charge of planning the army's movements, setting up traps, and devising battle plans to outwit the enemy.
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.
One possible reason could be the burden of his past. Naruto has faced a lot of hardships and the memories might be overwhelming him, making him want to be alone. For example, the loss of his master Jiraiya might have left a deep scar, and he might feel that isolating himself is the only way to deal with that pain.
Maybe he feels a sense of guilt. For example, if something bad happened in the village that he blames himself for, even if it wasn't really his fault. He could exile himself as a form of self - punishment. He has always been very hard on himself when it comes to the well - being of the village and his friends.