The sergeant, who's identification badge read: Sanchez, rolled forward and got back up to his knees behind a  another wrecked Warthog, followed by a pair of privates. All three of them ducked, pressed themselves against the Warthog, and then threw frag grenades over their heads. Their were three dull thumps, and a bird like chatter as Jackals were thrown to the ground by the shock wave from the grenades. Sanchez rose up, and began firing with his DMR.
“Hell, if any one should get a medal for this fight, then I say it would be that whacky Spartan kid, look at this damned destruction.”
Both of the Marines peered over the Warthog, and saw the sight of several fallen Covenant warriors, shattered barriers and downed turrets. Sanchez could still tell what the Marines were thinking: How the hell did he ever do such a thing?
Sanchez did not know, and at this moment he did not have time for it either. A pair of spec-ops Grunts fired their Needlers, and dozens of pink crystalline needles splattered the Warthog until most of the needles detonated and rocked the remnants of the Warthog so that one of the Marines fell to his back. Sanchez raised his DMR, and fired three shots at one of the Grunts, and it fell to the ground, dead as soon as the bullets landed on it's weak body armor. A Marine fired a burst from his assault rifle, and the second Grunt fell to a head shot.
“Where the hell did that spartan go?” A Marine asked as he fired his assault rifle at an Elite.
“I don't know, I'll try contacting him.” Sanchez said and tapped the comm open in his ears. “Spartan, this is sergeant Sanchez, where the hell are you? We have you nowhere in sight.”
“I'm right behind that small cliff forty meters from your current position. I'm taking down these Wraiths and I need backup.” Riko replied through the comm.
“We'll do our best sir, but these Covenant are not willing to give up easily. Out.” Sanchez said and shut down the comm. “He's taking out those Wraiths behind that hill, so let's clear a path and then-”
Their was a sudden wham, and crackle of energy in the air, and Sanchez was knocked over. He cursed, and tried to figure out what had just hit him. Their was a loud thud, and a Warthog landed ten feet behind him, it's passengers incinerated from an unknown force.
“Sergeant! Look, it's a slipspace portal!” A Marine yelled.
“What the?”
Sanchez looked upwards, and then saw that the Marine was true of his word. Their was a large slipspace portal formed into the air like a huge black hole, and their was something coming through it. Even the Covenant paused to look upwards at what was about to launch from that one, mysterious portal. Riko paused his aim through the scope of the Spartan Laser, and looked upwards. The portal had started to crack with electricity, and then a large white ball was formed into it's center, which grew steadily as the air began to smell as if time had halted for a second or two. Riko still looked up, not tearing his gaze from the skies. Then it all happened. A Covenant ship jumped from the portal, which was shut down behind it like a blast door as the huge alien craft emerged from slipspace. The Marines at the surface backed away, keeping their weapons raised, and the Elites and the other Covenant warriors turned back to their human adversaries and yelled a loud battle cry at them. Riko swore, and then watched as the shields of the Covenant ship lowered, and a flock of seven Banshee fliers came out, readying their pulse lasers and fuel rod guns. Riko had to choose his target now. He had only two more shots left for his Spartan laser, and their were still three Wraiths firing at the Marines. He screwed up any plans, this was war, and war took severe decisions to make. He aimed at one of the Wraiths, and then pulled down the trigger. The Spartan Laser whined, and then fired a hot red beam of laser at the flank of the Wraith. The alien tank shook, and then began to unleash sparks of energy from inside it as it fell to pieces one by one. Until it exploded in a ball of blue and white flame.
Three Elites now spotted Riko, and turned their plasma rifles at him, and fired. Several bolts struck the ground before him, but he avoided them. He aimed at the second Wraith, and charged up the Spartan Laser, and fired. The red beam punched through the Wraiths armor plating and then caused it to detonate like the one before it. But now the Laser was out of charges. He threw the weapon away, and drew his assault rifle, and began to run towards the third Wraith. In meanwhile, the Banshees began to open fire, and many Marines fell as pulse laser shots seared through their armor and flesh like butter. The battlefield was filled with the screams of the dying, and suddenly, things were not going well with the humans. A Warthog fired it's Gauss canon at a Banshee, and caused it to spin in the air, and then explode. But as the gunner rejoiced his kill, another Banshee fired it's fuel rod gun, and the Warthog exploded in a ball of fire and the driver and the gunner were both killed. Sergeant Sanchez pummeled a Jackal from his way as he advanced towards Riko's position with his two Marines, but suddenly Elites began to appear out of nowhere as they deactivated their active camo shields and charged from every flank of the Marine defenders. Sanchez fired four shots from his DMR, and his Marines emptied their clips into the Elites. But their was nothing they could do against a dozen energy swords and as soon as those blades hacked downwards, their was just a trio of screams and then then Sanchez and his men died.
Marines fell all over the place, and the UNSC defenses were failing as more and more Elites teleported from the ship above, and then charged the remaining humans with energy swords and plasma weapons in their hands.
Riko looked up at the Covenant ship, saw it's huge main gun begin to power up to fire. He sighed deeply, and as the Covenant ship continued to gather power, he knew it was all over. 
“Looks like were going first in to hell spartans.” Riko said and fired his weapon as Elites and Grunts closed in all over his position.