May 15th 2016 is when the portal opened and a thousand Zeti rushed through, then tens of thousands, then hundreds of thousands. All running straight to their deaths.
We always imagined aliens coming down from the sky with technology so advanced we would be slaughtered in a matter of days. That's not how it happened. The Zeti came through with spears and bows wearing only primitive leather armor. It was them getting slaughtered. Within 24 hours of the portal opening a Marine battalion had set up in front of the blue shimmering hole through space and time. As the days went by they never stopped coming. It didn't make any sense. A few made through the portal, saw the thousands of dead brethren then turned and hightailed it back to the other side, that's when we realized the door swung both ways. Then six days after it began, the invasion was over. Not a single Zeti came through.
The decision was made to send two drones through. One being a retrofitted bomb disarming robot and the other a standard military drone complete with extremely high end cameras and 4 Hellfire missiles. The bomb robot went through first and sent back images of a huge room with massive statues of creatures that were not the Zeti. It also showed an opening to the outside that a 747 could fly through so the other drone was launched. After clearing the doorway it rocketed into the sky and began sending back unbelievable images. Entire cities that looked like they belonged in the medieval era but with an alien twist.
After much deliberation the choice was made to send the battalion through. Whatever technology was inside that first room was worth the risk. Colonel Rike was chosen to lead the charge. What nobody knew at the time was Rike was in the midst of a complete mental breakdown. He hid it well.
As the troops poured through, every one wearing shoulder mounted cameras, they spread out to clear the building. Through a narrow doorway a small group Marines came upon what would later be known as the control room. In front of them was a massive hologram. It showed a central sphere with 56 lines coming out of it connecting to other spheres. All of them were a dull green except one. With video streaming back through the portal scientists and military commanders watched as the green line turned red as it neared a glowing orange sphere then the next one over began to glow. The moment the the red line hit what is now known as our planet the stream cut off and portal slammed shut.
The best minds in the world went over the video again and again. What they came up with was a shot in the dark. They believed that the Zeti were far too primitive to create this device. The statues of other creatures and the way the Zeti lived and fought just didn't add up. They believed the device could have been turned on by accident and is constantly jumping from one of the 56 planets to the next every seven days. They were right. 392 days from the first portal opening another popped into existence in the exact same spot.
The drone sent through sent back images that were almost too much to look at. Zeti hanging from posts, others digging massive holes that would become their own graves as soldiers stood guard and shot them for fun and "camps" with thousands of Zeti crammed in shoulder to shoulder, obviously starving. The camera zoomed in on a large stone temple that wasn't there a year ago and saw Colonel Rikes sitting on a golden throne.
Genocide. Not on humanitys watch. Not again.
Six F-22's ripped through the portal as just under the speed of sound, the drone painting targets and the planes finishing the job. Behind the planes 1000 troops advanced. It was strange killing humans on an alien planet but they had all seen the videos, edited perfectly with clips of the Nazi death camps so they could feel empathy for the aliens.
As a Marine Scout Sniper took aim at Rikes who was now hiding in the doorway of a burnt out shack his spotter asked him if he was okay with shooting a Colonel of his own military.
"When you've lost your humanity, you're no longer human." A second later the Colonels chest exploded as a .50 caliber bullet ripped through it.
As the last soldier who was "Just following orders" fell and the chains to the concentration camps were cut, high above the atmosphere humanity had just unknowing saved themselves.
A massive ship had been watching the carnage unfold. In a blink all the targeting reticules that had tracked every human, plane and drone vanished and a creature that looked just like the statues in the arrival room waved it's hand over a console, canceling a plot towards a planet called Earth.