The Marine base was next to the grounds where Zoro was held. Luffy went the wrong way previously.  

Ben in the middle, Luffy to his right and Alvida to his left walked towards the marine base. 

Luffy then shouted, “Come out Captain, I will beat you and save my crew member.”

Ben and Alvida, looked at each other. 

“I guess we are doing this the loud way,” Ben chuckled. 

At this moment, Helmeppo and Morgan appeared with two dozen marines soldiers behind them.

“Who's making all this noise?” Morgan shouted. Morgan was a tall, muscular man with tanned skin and blonde hair.  He wore  a large, ornate sleeveless overcoat. Most notably, he had an axe for one of his hands. 

Luffy charged at Morgan, punching him in the face.

Ben looked at the fight but turned towards his target, Helmeppo. Ben knew the story he knew was not this one. There were already some changes, maybe Helmeppo is slightly strong right now. 

Ben walked toward Helmeppo and smiled towards him. “I will be fighting you,” he said. 

“Don't get cocky with him,” said Helmeppo and drew a gun. He fired a shot and Ben dodged it. He looked back to remembering fighting the animals. Some of them were pretty fast. Ben felt the bullet come at him and moved to avoid it. He thought to himself, this may be the start of observation haki. 

Helmeppo was shocked to see Ben dodge it and ordered a dozen marines to charge Ben. The marines had swords with them and didn't have any rifles. Ben thought, budget shortage. 

The first marine tried to stab him with the sword from the front. Ben dodged and punched the marine in the face, knocking him out instantly. A second came from behind and tried to backstab Ben. Ben simply dodged towards the right and upper-cutted him. The marine went flying in the air and he was also knocked out instantly. After that four marines charged him from all directions. Benm simply jumped in the air to avoid their swords and started kicking the marine in a circular direction while in the air. All the marines' faces were hit by his kick. They all passed out.    

Seeing half a dozen of their fellow soldiers knocked out so easily put some fear in them. Ben then ran towards the remaining half dozen marine and beat them all with a single blow each to the chest.  The marines did try to defend themself however Ben was just too strong. 

Ben then talked towards Helmeppo. Helmeppo shot a few times but missed all. Partially because he was terrified and couldn't aim properly and partially because Ben was able to dodge them. Ben got to striking range and punched Helmeppo in the face, knocking him out. 

Ben thought, all one shotted, but this was fodder and the true heavyweight will not be this easy. The animals on that island were stronger than these marines here. 

At the same time, Alvida, using her massive  heavy, spiked Iron Mace to start clubbing the marines. Every swing she took she defeated three to four marines. She had taken out a dozen marines. She noticed the entrance and took off her slippers. Using her devil fruit she slid towards the entrance and into the main hallway. A marine tried to stop her but he used the iron mace to send him flying. Alvida, came across a room which stored all the swords. She looked in and found three swords lying on the table. She thought this must be it. Alvida grabbed the sword and slipped away towards Zoro. 

Meanwhile, Luffy and Morgan were fighting. Morgan was trying to slash Luffy but Luffy was too quick and dodged it.  “Gomu Gomu no Pistol” Luffy said as he hitted Morgan.

Morgan whimpered in pain and held his stomach. Luffy then follows up with another Pistol attack sending Morgan towards the grounds where Zoro was. 

Zoro sees Morgan getting up. Alvida slips onto the battlefield and throws the swords in the air. Zoro catches one of the swords with his mouth and attacks the cross. He has broken free. He picks up the other sword and charges towards Morgan. Morgan blocks Zoro's attack with his axe. 

Zoro smiles and attacks with his sword again, slicing him this time on the chest.  Luffy then comes charging towards Morgan and shouted, “Gomu Gomu no Bazooka.” The attack hits Morgan straight on and he is sent flying in the air. Morgan is defeated before he even hits the ground.