Attack on the HYDRA Research Base

"Report to your stations immediately. This is not a drill. We are under attack. We are under attack."

- Wolfgang von Strucker to HYDRA Soldiers

The Attack on the HYDRA Research Base was the final confrontation between the Avengers and Wolfgang von Strucker's HYDRA branch. The attack successfully ended the War on HYDRA.

Background
"I'm guessing HYDRA doesn't know that Loki's Scepter was the weapon that killed me, but I bet they know it can control minds." "In their hands that's catastrophic; Coulson please tell me you know where it is." "Sokovia, pretty sure List is headed there right now."

- Phil Coulson and Maria Hill

During the Attack on the Arctic HYDRA Research Facility, S.H.I.E.L.D. Director Phil Coulson downloaded important files and data about HYDRA's activities. It contained the location of Wolfgang von Strucker and his illegal experimentation on human subjects. These files revealed also the presence of the Scepter. After the battle and destruction of the Arctic HYDRA Research Facility, Coulson sent the information to Maria Hill during a private conversation and asks her to bring the Avengers to attack the Sokovian HYDRA fortress.

Later, the Avengers agreed to launch a surprise attack against the HYDRA Research Base to foil HYDRA's plans to dominate the world.

Perimetral Defenses
"We will not yield. The Americans send their circus freaks to test us. We will send them back, in bags. No surrender!"

- Wolfgang von Strucker

The Avengers arrived in the snowy terrain somewhere near the HYDRA Research Base. Black Widow drove a truck through the perimeter as Hawkeye stood on the back seat, shooting the HYDRA soldiers one by one. Iron Man tried to fly directly into the base, only to be repelled by the advanced shielding guarding it. J.A.R.V.I.S. revealed that the technology at this base was more advanced than any other HYDRA base they had yet encountered. Inside the castle, Baron Wolfgang von Strucker was briefed on the situation. Learning that his troops had panicked upon realizing they were under siege by the Avengers, von Strucker ordered the staff to send the rest of the tanks and soldiers and ordered them to concentrate fire on the weaker ones, as a hit would force them to close ranks. He discussed with List the amount of research they had done; the latter tried to convince him to send the twins, Wanda and Pietro Maximoff. Von Strucker refused, saying they were not ready for battle. He restated his confidence that his men could contain the Avengers.

The soldiers began to fire at Iron Man, and shells started to hit Novi Grad. Iron Man responded by sending the Iron Legion to evacuate civilians. Encountering some resistance from the local population, the Legion successfully evacuated most of the area.

Shortly afterwards, back at the base, Strucker delivered a speech to his men, telling them that they will continue to fight and will not surrender. Privately, he told List that he planned to surrender, and asked him to wipe all data from the base's computers. He rationalized this by saying that if they would hand over all the weapons to the Avengers, they might overlook what else is left at the base. Before List could take any action, both of them realized that the twins were missing.

In the forest, Hawkeye tried to destroy another HYDRA bunker, but encountered Pietro Maximoff: Quicksilver. Quicksilver used his super speed to activate the turrets on top of the bunker, injuring Hawkeye in the process. Quicksilver then engaged Captain America, using his speed to his advantage. Captain America relayed the information to Stark about the arrival of powered people on the battlefield.

Breaching the Facility
"Baron Strucker. HYDRA's number one thug." "Technically, I'm a thug for S.H.I.E.L.D."

- Captain America and Baron Wolfgang von Strucker

Shortly afterwards, Iron Man successfully deactivated the shield around the facility by destroying the power source in the north section. He broke into the facility, quickly neutralized the remaining soldiers, and shot List with a repulsor blast before the latter could wipe all the data. Stark exited his armor, placed it in an automated sentry mode, and tasked J.A.R.V.I.S. with making a copy of all remaining data, which was to be sent to Maria Hill back at Avengers Tower. In the forest, most of the HYDRA soldiers surrendered. Black Widow approached Hulk and touched his hand, reciting the lullaby which calms him enough to revert back to Banner.

Inside, Stark realized the facility held more than just files and data as he found a secret passage underground. Elsewhere, Captain America found and confronted Baron Wolfgang von Strucker about the Scepter and the human experimentation occurring in the facility, only to be attacked by Wanda Maximoff, or the Scarlet Witch, who quickly fled the scene. Receiving no answer, Rogers quickly subdued Strucker. Underground, Stark arrived at a lab, housing Chitauri Armor, Chitauri Guns, and even a Leviathan, all recovered from the Battle of New York. He found the Scepter, but before he could grab it, he was attacked by Scarlet Witch, who managed to sneak up behind him. As the hallucination took shape, his worse fears appeared to come to life: the Leviathan started to move and flew over him. Following it with his eyes, he turned around and saw himself in Chitauri Space, his teammates dead in front of him. Steve Rogers briefly opened his eyes, telling Stark that he could have saved them all. Stark looked up and saw a Wormhole to Earth, with several Leviathans and Chitauri flying through it, ready to attack. He woke up from his trance, summoned his armor gauntlet, and grabbed the Scepter.

Aftermath
Most of the HYDRA soldiers were either killed or surrendered on the battlefield. NATO forces arrived in the Avengers' wake and imprisoned Wolfgang von Strucker, while the team itself retrieved the Scepter.

Tony Stark was left affected by the visions he had seen, and was even more adamant about finishing the Ultron Program.

The HYDRA Research Base was abandoned until Ultron returned to create a new body for himself and take over the sentinels created by HYDRA.