The Secret Service were the first men who ever used the teleport technology. The very first who came to God's Sanctuary were not Han Jingzhi and the ancestor of the Nings, but ordinary crewmembers.
After they arrived at God's Sanctuary, they found something and had a few accidents. Only two persons made it back to the Alliance.
Those two persons reported what they found on the other end, which made everyone overjoyed. Very soon, the second unit was sent through the same way.
This time, the personnel dispatched were no longer ordinary crewmembers, but a unit made up of elite. There were eleven in total, which included the instructor of the Blueblood Special Force, Instructor Han.
That unit was Unit 7.
The unit stayed in God's Sanctuary for less than seven days. Less than half of them made it to the Alliance, which included Han Jingzhi and the ancestor of the Nings.