Well, here's my theory from Half-Life 1 and how it leads into Half-Life 2. First, though, the basic plotlines of HL1, Opposing Force and Blue Shift should be considered. Anything important is marked in bold.
HALF-LIFE:
- Scientist (Gordon) performs a test using an unknown crystal and a super-charged spectrophotometer-thingy.
- Experiment goes wrong, something with the crystal causes it to rip open dimensional portals everywhere.
- Scientist fights his way through the compound.
- Apparently, government troops are dispatched to kill everything.
NOTE: This is the first minor implication that the government already knows about these aliens. Although most people might not pick it up, it's slightly odd that the government would have dispatched such heavily armed soldiers to a scientific research lab. Furthermore, this is confirmed in Opposing Force.
- Eventually, Freeman finds a scientist who has a device to take him to Xen.
NOTE: This is the first strong implication that we've already been to Xen. Before this, there is no really emphasized implication that humans have visited the Xen world.
- Freeman fights through Xen, encountering dead (HEV Suit) humans along the way.
- Freeman defeats the Nihilanth, supposedly crippling the alien forces, and allowing the G-Man to take over.
Now, the first thing is obviously that the government wanted Xen experimentation for some military use. Whether it be to harvest the aliens as troopers or to use it as an instant teleporter thing, they wanted it.
One of the most interesting things were what the Nihilanth was saying.
He quite clearly says several things in English.
"YOU ARE MAN HE IS NOT MAN FOR YOU HE WAITS FOR YOU"
"THE TRUTH YOU CAN NEVER KNOW THE TRUTH"
"FREEEEEEEEEEMAN!"
Now, it's pretty easy to figure out that the "not man" waiting for you is the "G-Man". So what's the truth? Well, since you can never know it, then the G-Man must be lying. The Nihilanth obviously knows what's going on, since he knows that the G-Man is running the show and that your name is Freeman.
The Nihilanth could know this information any of four ways:
1) Telepathy - He can read minds. This seems quite unlikely, since if he could read your mind when you were in another dimension, he could certainly read your mind in Xen - and thus, send about a million aliens to go kill you. So I don't find this very likely.
2) Aliens - Another theory is that the aliens report back what they see and hear. Again, not entirely likely - since the Aliens probably wouldn't know that the G-Man is waiting, that he is lying, and that your name is Freeman.
3) Someone Told Him - But who? Probably nobody.
4) Prior History - The Humans have had a relationship of undefined length with Xen aliens. They obviously have met - but we don't know for how long. The only really logical conclusion is that the humans betrayed the Xen aliens. The G-Man might even had been some sort of alien generated to be quasi-human that defected, but there's not a lot of information to prove that. However, this seems like the most obvious choice.
So, we know that the Nihilanth knows a lot, the G-Man knows a lot, the Government knows a lot, but you know next to nothing. You know you're being lied to by the G-Man and the Nihilanth attempted to tell you that.
Now, onto Opposing Force -
OPPOSING FORCE:
- Prelude - In the manual (I believe) it states that you have been doing very odd indoor training exercises for weeks. This makes it extremely obvious that the government had very advance knowledge, and that they even planned the Black Mesa Incident. It would have been a gamble but a very good plan - if the Xen creatures were threatening to rip open a portal to the world, it may be best to create the Black Mesa Incident, and then kill the Nihilanth using Freeman and/or Marines.
- The Marines' planes are shot down over Black Mesa. Adrian awakens and starts kickin' butt.
- You discover neat weapons, ones not in Half-Life: things like the displacer gun, etc. This makes it obvious that there was LOTS of portal research. The Displacer Gun is apparently 100% human tech - perhaps the humans came upon Xen this way?
- Adrian stays in Black Mesa during the time when Freeman is fighting the Nihilanth. When Adrian destroys his foe, the G-Man gives him a speech similar to Freeman. Black Mesa is then nuked.
Now, you'll note that this chapter effectively served to show the extent of the human's knowledge of Xen. It's now been directly confirmed that humans have known about Xen for a very long time. It also backs up and confirms that the G-Man controls a good deal of the US Army with indeterminate but very high authority.
BLUE SHIFT:
Nothing really important here... however, there is one big point.
- Portals REQUIRE crystal, and humans were entering Xen on a constant basis to retrieve the stuff. In fact, it has been going on for so long, they built the current base on the old one! It can then be assumed the displacer gun contains a crystal and uses it as "Ammo". This also suggests that crystals are "used up" with each transport. The rapid harvesting of crystals implies that the humans were trying to use Xen as a transport medium.
HALF-LIFE 1 THEORY:
Based off this information, it appears as if the humans found Xen by some teleportation means (perhaps a pseudo-crystal) as they were trying to develop an effective site-to-site transfer device. When they found out that their medium contained a new race, they may have done some form of diplomacy, or something - probably involving the G-Man. Then, of course, relations broke down as humans went to relentlessly capture crystals. The government had the idea of opening a big portal in order to kill the Nihilanth and thus subjugate Xen. This is precisely what they did, as indicated by their preparations. It worked to an extent - Freeman killed the Nihilanth, and him and Adrian Shepherd are contracted by the G-Man.
So where does it fit in that the G-Man is not human?
Well, he's not human... says the Nihilanth.
He's obviously not a Xen creature.
So what is he? Perhaps, a combination of human/alien? Or human/machine? The Combine.
HALF-LIFE 2
Now, Half-Life 2 starts. Gordon has been in some kind of statis for 10 years... meanwhile, the Combine is raising hell all over. The G-Man sends you out on a mission, presumably to stop the Combine.
It's my theory that he works for some third-party group that's related to the Combine but not it. Perhaps he was the result of some Government experiment - or, maybe not. Either way, he's not human and he's not Xen and he's not Combine. The only logical meaning would be that the G-Man is something related to the Combine. Also note that he hasn't aged since 10 years ago... although the graphics are new, you can quite obviously see that he is near the same age.
So what about the Combine?
It's hard to link the events at Black Mesa to the Combine. The only thing I can come up with that's logical is that the government wanted to create some human/alien/machine hybrid, which was the Combine, which then got out of control.
This would explain the G-Man. The G-Man was the first Combine entity, the Government project to make a super-man and a super-soldier. It must have gone wrong sometime between the Black Mesa incident and City 17 Incident.
--------------------
FINAL CONCLUSIONS
--------------------
The Combine - The Combine were a project to meld human/machine/alien into some sort of super-soldier. They went renegade at some point and started tearing stuff up.
Xen Monsters - They're also tearing things up in the future, probably due to some transport mishap or new Nihilanth, or maybe just government fault.
US Government - Tried to use Xen for a medium through which to transport troops, ended up going to war with Xen monsters. They had two plans -
-- Black Mesa
Kill Nihilanth through Black Mesa.
-- Combine
Create super-soldiers through human/machine technology.
G-Man - The first Combine prototype. Works for the US Government. Pretty much de facto power when it comes to Xen - probably very high up.
Dr. Kleiner - He shows up in HL2. This is guy to look out for - he was responsible for Freeman's transfer, AND for Barney Calhoun's assignment to Black Mesa...
So what do you guys think?
HALF-LIFE:
- Scientist (Gordon) performs a test using an unknown crystal and a super-charged spectrophotometer-thingy.
- Experiment goes wrong, something with the crystal causes it to rip open dimensional portals everywhere.
- Scientist fights his way through the compound.
- Apparently, government troops are dispatched to kill everything.
NOTE: This is the first minor implication that the government already knows about these aliens. Although most people might not pick it up, it's slightly odd that the government would have dispatched such heavily armed soldiers to a scientific research lab. Furthermore, this is confirmed in Opposing Force.
- Eventually, Freeman finds a scientist who has a device to take him to Xen.
NOTE: This is the first strong implication that we've already been to Xen. Before this, there is no really emphasized implication that humans have visited the Xen world.
- Freeman fights through Xen, encountering dead (HEV Suit) humans along the way.
- Freeman defeats the Nihilanth, supposedly crippling the alien forces, and allowing the G-Man to take over.
Now, the first thing is obviously that the government wanted Xen experimentation for some military use. Whether it be to harvest the aliens as troopers or to use it as an instant teleporter thing, they wanted it.
One of the most interesting things were what the Nihilanth was saying.
He quite clearly says several things in English.
"YOU ARE MAN HE IS NOT MAN FOR YOU HE WAITS FOR YOU"
"THE TRUTH YOU CAN NEVER KNOW THE TRUTH"
"FREEEEEEEEEEMAN!"
Now, it's pretty easy to figure out that the "not man" waiting for you is the "G-Man". So what's the truth? Well, since you can never know it, then the G-Man must be lying. The Nihilanth obviously knows what's going on, since he knows that the G-Man is running the show and that your name is Freeman.
The Nihilanth could know this information any of four ways:
1) Telepathy - He can read minds. This seems quite unlikely, since if he could read your mind when you were in another dimension, he could certainly read your mind in Xen - and thus, send about a million aliens to go kill you. So I don't find this very likely.
2) Aliens - Another theory is that the aliens report back what they see and hear. Again, not entirely likely - since the Aliens probably wouldn't know that the G-Man is waiting, that he is lying, and that your name is Freeman.
3) Someone Told Him - But who? Probably nobody.
4) Prior History - The Humans have had a relationship of undefined length with Xen aliens. They obviously have met - but we don't know for how long. The only really logical conclusion is that the humans betrayed the Xen aliens. The G-Man might even had been some sort of alien generated to be quasi-human that defected, but there's not a lot of information to prove that. However, this seems like the most obvious choice.
So, we know that the Nihilanth knows a lot, the G-Man knows a lot, the Government knows a lot, but you know next to nothing. You know you're being lied to by the G-Man and the Nihilanth attempted to tell you that.
Now, onto Opposing Force -
OPPOSING FORCE:
- Prelude - In the manual (I believe) it states that you have been doing very odd indoor training exercises for weeks. This makes it extremely obvious that the government had very advance knowledge, and that they even planned the Black Mesa Incident. It would have been a gamble but a very good plan - if the Xen creatures were threatening to rip open a portal to the world, it may be best to create the Black Mesa Incident, and then kill the Nihilanth using Freeman and/or Marines.
- The Marines' planes are shot down over Black Mesa. Adrian awakens and starts kickin' butt.
- You discover neat weapons, ones not in Half-Life: things like the displacer gun, etc. This makes it obvious that there was LOTS of portal research. The Displacer Gun is apparently 100% human tech - perhaps the humans came upon Xen this way?
- Adrian stays in Black Mesa during the time when Freeman is fighting the Nihilanth. When Adrian destroys his foe, the G-Man gives him a speech similar to Freeman. Black Mesa is then nuked.
Now, you'll note that this chapter effectively served to show the extent of the human's knowledge of Xen. It's now been directly confirmed that humans have known about Xen for a very long time. It also backs up and confirms that the G-Man controls a good deal of the US Army with indeterminate but very high authority.
BLUE SHIFT:
Nothing really important here... however, there is one big point.
- Portals REQUIRE crystal, and humans were entering Xen on a constant basis to retrieve the stuff. In fact, it has been going on for so long, they built the current base on the old one! It can then be assumed the displacer gun contains a crystal and uses it as "Ammo". This also suggests that crystals are "used up" with each transport. The rapid harvesting of crystals implies that the humans were trying to use Xen as a transport medium.
HALF-LIFE 1 THEORY:
Based off this information, it appears as if the humans found Xen by some teleportation means (perhaps a pseudo-crystal) as they were trying to develop an effective site-to-site transfer device. When they found out that their medium contained a new race, they may have done some form of diplomacy, or something - probably involving the G-Man. Then, of course, relations broke down as humans went to relentlessly capture crystals. The government had the idea of opening a big portal in order to kill the Nihilanth and thus subjugate Xen. This is precisely what they did, as indicated by their preparations. It worked to an extent - Freeman killed the Nihilanth, and him and Adrian Shepherd are contracted by the G-Man.
So where does it fit in that the G-Man is not human?
Well, he's not human... says the Nihilanth.
He's obviously not a Xen creature.
So what is he? Perhaps, a combination of human/alien? Or human/machine? The Combine.
HALF-LIFE 2
Now, Half-Life 2 starts. Gordon has been in some kind of statis for 10 years... meanwhile, the Combine is raising hell all over. The G-Man sends you out on a mission, presumably to stop the Combine.
It's my theory that he works for some third-party group that's related to the Combine but not it. Perhaps he was the result of some Government experiment - or, maybe not. Either way, he's not human and he's not Xen and he's not Combine. The only logical meaning would be that the G-Man is something related to the Combine. Also note that he hasn't aged since 10 years ago... although the graphics are new, you can quite obviously see that he is near the same age.
So what about the Combine?
It's hard to link the events at Black Mesa to the Combine. The only thing I can come up with that's logical is that the government wanted to create some human/alien/machine hybrid, which was the Combine, which then got out of control.
This would explain the G-Man. The G-Man was the first Combine entity, the Government project to make a super-man and a super-soldier. It must have gone wrong sometime between the Black Mesa incident and City 17 Incident.
--------------------
FINAL CONCLUSIONS
--------------------
The Combine - The Combine were a project to meld human/machine/alien into some sort of super-soldier. They went renegade at some point and started tearing stuff up.
Xen Monsters - They're also tearing things up in the future, probably due to some transport mishap or new Nihilanth, or maybe just government fault.
US Government - Tried to use Xen for a medium through which to transport troops, ended up going to war with Xen monsters. They had two plans -
-- Black Mesa
Kill Nihilanth through Black Mesa.
-- Combine
Create super-soldiers through human/machine technology.
G-Man - The first Combine prototype. Works for the US Government. Pretty much de facto power when it comes to Xen - probably very high up.
Dr. Kleiner - He shows up in HL2. This is guy to look out for - he was responsible for Freeman's transfer, AND for Barney Calhoun's assignment to Black Mesa...
So what do you guys think?