--- December 25, 2029, Army Cadet Preparatory School. Campinas, São Paulo, Brazil. ---

Pedro is in his dormitory putting on his military uniform and equipment, his roommates are all agitated. Nobody knows what's happening, but an order for everyone to prepare and wear their gear has been issued.

"Hey, what do you think is going on?" Gabriel asked with an excited smile as he put on his helmet.

"I don't know," Pedro replied, "but if you're already ready, let's go to the courtyard and find out."

Everyone leaves the room, fully dressed in uniform, the weight of their backpacks nothing compared to the pressure everyone was feeling at that moment. As they reached the courtyard, they all formed up, about 450 Cadets were present, along with some officers, all in uniform and with their IMBEL IA2 assault rifles. In the background, sounds of gunfire and artillery could be heard coming from the city, these sounds started not long ago, Pedro thought it could be some military exercise in the outskirts of the city. It had been a few minutes since the last Cadet entered formation, but suddenly General Marcelo broke the silence, causing all the Cadets to look at him.

"Firstly, I want to inform you gentlemen present here that this is not an exercise," they all looked confused at each other and at the general. Pedro looked at Gabriel, and there was no longer the smile from moments ago on his face, but rather a serious expression. "I'll get straight to the point, the city of Campinas is under attack by an unknown enemy force." A pallid look fell upon all the cadets present there. Pedro felt a knot in his stomach and a sense of fear and discomfort that couldn't be avoided upon hearing this from the mouth of one of the generals he respected most in the country; he knew something was happening, but not to this extent. "Please, gentlemen, I ask that you remain calm and exercise your professionalism now. We have reports that the enemy force emerged from a portal that suddenly opened in the city center; we have no precise details about their forces, but they consist of mythological beings and all sorts of horrendous creatures. There are also reports of soldiers dressed in metal armor and men mounted on horseback trampling everything in their path." As the General spoke, you could feel the fear among the other cadets, but everyone remained silent.

The General passed the word to a Lieutenant Colonel beside him. "From what you have heard, the situation is critical. The enemy has advanced deeply into the city, and about 20% of the city is already under enemy control; the number of casualties is still unknown. Unfortunately, we have lost the City Hall; there are no reports of survivors in the building. The police are doing everything to stop the enemy's advance. For now, they are managing to hold their positions and prevent the enemy's advance from continuing, but unfortunately, they won't last much longer at this rate. That's why we have authorized all of you to join the Eleventh Mechanized Infantry Brigade (Anhanguera Brigade) to help stem the enemy's advance while we await reinforcements." After this brief update on the facts, the cadets were given IMBEL IA2 rifles and all remaining equipment; within half an hour, everyone was already on board one of the Guarani armored personnel carriers. Inside the vehicle, there was complete silence, with only the sounds of engines and muffled gunfire from outside.

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Gabriel was the first to speak. "What do you think they are?" His question made the other 10 crew members look at each other, unsure of the most logical and appropriate response to answer that question.

"Aliens," one of the soldiers said.

"Aliens in armor?" one of the cadets asked, mocking his colleague's assertion.

Pedro would like to keep logic always in the forefront, but all this situation is making him uneasy.

"And you, what do you think they are?" one of the cadets asked Pedro.

He looked at his rifle, thinking of a response.

"The only thing that seems certain now is that they are not from our world and are killing people in the streets and destroying the city." Everyone looked at Pedro; they knew he was right, but hearing this statement from one of the top-scoring students at the Military School was chilling.

--- Francisco Glicério Avenue ---

The armored vehicle suddenly stopped as they reached the avenue that provides direct access to the city center. At this point, the sounds of gunfire and artillery were even louder. When the light inside the vehicle turned green and the rear door opened, they knew that the battle was about to begin, and finally, some of their questions would be answered.

Upon exiting the Guarani, it was possible to see that the vehicle had stopped because a huge line of cars had created a traffic jam in an attempt to leave the city. Some were abandoning their cars and running as far away as possible from whatever was coming in the opposite direction. One of the cadets saw a woman with blood all over her forehead being helped to walk by a teenager. He then ran to help.

"Please, help my grandma!" said the girl as she cried.

Witnessing this scene, Pedro and Gabriel looked at each other; any uncertainty about what was really happening was dead. A sergeant appeared and shouted an order to the cadets, "You, accompany the Guarani while it clears a path through the vehicles; all civilians have abandoned their vehicles and are running along the sidewalks of the avenue, so be careful when firing cover shots.

While the Guarani continued to clear the way, the number of civilians running in the opposite direction of the cadets had ceased. All they could see now were bodies of civilians on the ground. The armored vehicle stopped at a police defensive barrier formed by cars, along with the other three Guarani armored vehicles that were coming right behind. The Guarani were accompanied by 10 more Guaicuru 4x4 armored vehicles (LMV-BR) and a Centauro 2 tank destroyer.

A policeman who was in charge of the vehicle barrier approached the sergeant who had just stepped out of the LMV-BR. "We've lost contact with the third police defense line 1km from here," said the policeman as he checked his pistol. "How many officers were there?" asked the sergeant as he listened to the increasingly intense sounds of gunfire in the city. "About 157 officers were at that defense post." Pedro listened to the conversation and noticed the pale face of the sergeant whose name he barely knew.

"That means we're the last line of defense between them and the rest of the city," the sergeant checked his 7.62mm ammunition magazine to see if it was fully loaded, and then looked at the rest of the armored column. "We will defend this post with our lives, understood?" shouted the sergeant. All that could be heard was a "Yes, sir" from everyone present.