Read before watching
There are two versions prepared of this speedrun. One is with only the gameplay (no cutscenes) and the other is with the cutscenes included. Both versions have all the segments appended into one file. The cutscenes are pretty entertaining and worth checking out if you have the time. Be aware that some missions are skipped, so the mission briefings sometimes appear to come slightly out of the blue.

About dosbox and the system
This run was done in dosbox (0.74-3). There are issues with running this game on a modern computer in dosbox. It's a resource-demanding game and dosbox doesn't benefit from all the power a modern computer is packed with. Dosbox only utilizes one CPU core and doesn't benefit from the graphics card (although the graphics card will of course influence the capture). There are no specific minimum requirements, so I'm just listing mine and it can then be used as reference for system and quality if anyone wishes to play this game. I have an i5 2330 (3 GHz, 4 cores) CPU sitting in a G3610 motherboard and 8GB of RAM. Dosbox runs in Windows 10 on an SSD. The recording is done with my GTX 760's recording software, Shadowplay.

Background
I remember having a really good experience playing through this game not long after it was released. The gameplay is great, the missions are fun, challenging and varied enough to keep it interesting and the cutscenes are exaggerated in a humorous way. When starting to get into speedruning, this is one of the games I've been wanting to see a speedrun for.

While this game generally gets good reviews and is well-liked by those who've played it, it's hardly a popular game. There are no re-releases of it (nor have I found any traces of one being in the works either) and the original game doesn't run on modern computers. The easiest way to play it is therefore through the means of e.g. emulation. Unfortunately, it's quite a demanding game and not any modern system will run it smoothly.

I started planning a speedrun in 2017. When routing the game, I was positively surprised by the amount of speed strats it had to offer. Many of the strats were also consistent enough that a single-segment run on 'difficult' difficulty (second hardest) seemed like a good option. The main problem was how to get the game to run well enough to record something of an acceptable quality. I did complete a few attempts, but eventually decided to abandon because the recording quality was so bad. I did get back to the game a few times and tried to play around with various settings, but didn't manage to do much to improve the quality.

Earlier this year (2019), I bought a new computer and wanted to see if the situation had changed. The actual recording of the gameplay now runs smoother thanks to a better graphics card, but the game itself unfortunately still doesn't run well enough. With a single-segment not looking possible with my setup, I decided to instead try a segmented run. Since most missions are very short, I was hoping that it would be possible to get an acceptable quality by redoing them enough times. A segmented run also allowed for playing on 'extreme' difficult (hardest setting) to make it more interesting.

About the difficulties
There are four difficulty settings in this game, 'easy', 'normal', 'difficult' and 'extreme'. In the first two, you can't access the full game and they are therefore of less interest. Compared to 'difficult', 'extreme' difficulty has many more enemies, you take more damage, enemies are more aggressive, enemies take less damage and then there are some minor differences/oddities such as a thunderbolt in 3-5 not being present. Finally, there are a few oddities such as the boss in 1-2 dying from one thunderbolt on 'extreme', while it takes more hits on 'difficult'.

Speed tricks
* Thunderbolts (special weapon) - It's basically a powerful missile, but with an additional feature. Upon impact, it will split up into several fireballs that will drop down to deal additional damage. These fireballs can go through walls and energy shields, allowing you to destroy things earlier than what's (supposedly) intended.
* Smartbombs (special weapon) - Shoots out homing missiles on all visible enemies within a certain range. There is no special feature, but smartbombs can reduce the completion time of some missions by a lot.
* Descending cliff walls - As long as a cliff is not vertical, you can descend it when in the tank by positioning yourself correctly and then turn while falling.
* Climbing walls - A few places allow you to climb along wall seams when in the tank to create shortcuts.
* Drop manipulations - Many enemies have a low probability of dropping weapons. I haven't found any pattern to this, but at least in a segmented run, a few missions are worth being redone until the right drops appear.
* Secret areas - There are many caches with extra weapons and health hidden throughout the game. Even though they require detours, many of them are worth visiting for stocking up and healing to allow for faster solutions in later missions. A list of the known secrets: http://www.mogelpower.de/cheats/loesung.php?id=5632&pf=99
* Mission skips - There is a warp in 1-1. In 3-6 and 4-2, you can complete the objective of the following mission, effectively allowing you to skip one mission.
* "Bichording/straferunning" - Strafing while moving forward adds a speed boost of around 5%. Moving up or down doesn't seem to impact the speed.
* Mission health refills - If the health is below a certain threshold, the the health will be refilled to this minimum level at the start of the next mission.

Run comments
Since the segments have been appended into one file, time stamps have been included below. The first time stamp refers to the start of the mission in the version without cutscenes and the second to the start of the mission with cutscenes.

1-2 (0:18/1:23)
The first of many uses of the thunderbolt. The boss is behind a energy shield that is powered by three generators that normally need to be destroyed before the boss can be damaged, but the fireballs from the thunderbolt deal damage without destroying the triggers. Interestingly enough, one thunderbolt destroys the boss on 'extreme', but not on 'difficult'.

2-1 (0:24/2:01)
A laser cannon drop was manipulated from the mines right at the start. The amount of ammo increases the firing rate and therefore speeds up the next missions.

2-9 (4:13/9:45)
Taking out all targets with one smartbomb is not completely consistent, but my setup still has a fairly good success rate. I back up and rise until the first target circle is close to the bottom of the bar with the scrolling mission objective. Then I fly straight up for a second or so. Then straight ahead. When all the targets are marked, launch the smartbomb. The target that most often slips away is the first one on the right side. It often helps to wait a little after all the targets have been marked.

3-2 (4:35/11:44)
The path used to complete this mission is normally a dead end because of the energy shield at the end and the generator powering it being on the other side. However, this is solved by using a thunderbolt, opening up the path at the end to trigger the mission end.
The objective is to work your way through the complex and get back to the outside again. There is a different (and longer) path leading you to the outside. Once outside, you can destroy said generator with your normal weapons and get back inside to access the same area as shown in this run.

3-4 (6:18/14:19)
Good thing the prisoners were able to survive a direct hit from a thunderbolt on their cage...
A missile drop was manipulated from one of the enemies.

3-6 (7:40/16:51)
The mission objective is to collect the alien weapon and bring it back out of the cave system. Once you do that, you're ordered to get back in and destroy a power generator. However, the generator appears shortly after collecting the weapon. By destroying, the whole trip out and then back into the cave was skipped.

3-8 (9:06/19:05)
As far as I can tell, you need to get 7 "points" to pass this mission. Bug enemies are worth one, while enemy helis seem to only count as half.

4-1 (11:36/23:37)
One of the most difficult missions of the run. There are lots of enemies and most of them will chase after you if you don't destroy them. Many of the hits are more or less mandatory and the health will always be very low at the end. Considering the difficulty of this segment, I'm mostly happy with how it turned out and I even managed to get a random missile drop from one of the enemies (4-3 would have been problematic without this missile). Unfortunately, the recording is bad at the end of the mission due to lots of stuff going on. If this had been an easier segment and not requiring the missile drop, I would have tried to get a better recording, but I eventually decided to settle for this.

4-3 (12:55/25:38)
The thunderbolt half-way through hit one of the pillars and one of the resulting fireballs destroyed a power generator at the bottom of the shaft. This lowered the bridge.
By driving off the ramp half-way up, you can reach the end zone and trigger the mission end while falling.

4-4 (13:31/26:55)
The intended way is to go over the bridge and then a long way around by spiraling down to the bottom. However, with careful positioning, you can descend the first cliff face and end up right at the exit. The setup I use is pretty consistent and consists of driving off the bridge onto the cliff face a little above horizontal.
Full health is pretty much required in the next mission, so a small detour was done by destroying the light beam robot and then collecting the health drop.

4-5 (13:55/27:45)
There is a trigger to remove the barrier to the bridge, but it's easy to bypass the barrier and get onto the bridge. Other than saving time, this also means the enemy tanks aren't activated.
The first tank after the bridge gave me a lucky missile drop, which was needed for a later mission (5-2).
Near the end, a small shortcut was taken by climbing up to the exit via a seam instead of following the path.

4-6 (14:52/29:13)
Visiting a secret area at the very start works as a shortcut for this mission.

4-8 (15:26/31:12)
If you're close enough to the replication machine while zapping the first power generator, you'll insta-clear the mission. While this saves 6-7 seconds, it will also skip the smartbomb and health in the secret area at the end (since a thunderbolt was used on the second generator and one was collected in the secret area, those level each other out). While it should be possible to get through 4-9 with low health, I don't see any smartbomb uses that saves less time than this.

4-9 (15:53/32:21)
Minor shortcut at the end, similar to the one in 4-3. By driving off the ramp, you can reach the mission end trigger while falling.

5-2 (17:07/36:15)
It took a while to find a consistent setup for taking out all the targets on the lower plateau with two smartbombs. Fly more or less straight and drop down in height to the level of the upper plateau. When the brown patch of the lower plateau is almost covered by the cockpit, turn hard right and then launch a smartbomb when the rightmost target is at the edge of the mini-map between 10 and 11 o'clock. This should take out the first 8 targets. The positioning here is pretty specific, but it's consistent. Taking out the second set of enemies with a smart bomb is easier.
The major issue with this mission is to get a missile drop, but with the route shown in the video, you'll get within range of a few destroyed enemies and therefore have a few chances each attempt.

5-5 (18:32/39:55)
There is a minor oddity at the end of this mission. There is a blue turret at the entrance of the temple that drops a thunderbolt. On 'difficult' difficulty, the turret is there at the start of the next mission (unless destroyed by the smartbomb during this mission) and you can therefore end this mission earlier. However, the blue turret is always gone in the next mission on 'extreme' difficulty and a few extra seconds are therefore spent on collecting the thunderbolt already now.

5-6 (19:25/41:19)
The objective of this mission is to destroy a well-protected power generator inside the temple. A thunderbolt is fortunately able to destroy it through the wall, avoiding to deal with some enemies dealing a lot of damage.

5-8 (20:30/43:34)
The intended way to beat this mission is to fight your way through a heavily guarded level and destroy a power generator at the end. However, once again the thunderbolt completely destroys the mission. I haven't found a consistent setup for destroying the generator with one thunderbolt. Obviously no problem in a segmented run, but in a single-segment run it's advisable to reserve two thunderbolts for this mission, which guarantees mission completion.

5-9 (20:36/44:30)
It's important to position yourself sufficiently far away from the UFO. Otherwise turrets on the ground and missile robots will be activated.

6-1 (21:15/46:15)
Very tough mission. The first tunnel is littered with enemies that deal a lot of damage. The biggest problem is to get past the light beam robot after the first energy shield. I did not find a consistent way to do this and was basically just brute-forcing my attempts and hoping to get through that part with enough health left for the rest of the mission.
The thunderbolt used after the light beam robot destroyed three generators powering the next energy shield and saving quite a lot of time (not to mention that it would have been next to impossible to take them out one by one without running out of health).

6-2 (22:17/48:09)
There are two generators placed around the level that controls the energy shield for the main generator in the middle. Fortunately, a thunderbolt is enough to destroy it without having to deal with the other two generators. So another mission that's made trivial by a well-placed thunderbolt.

6-4 (22:36/50:33)
The smartbomb has to be launched somewhat specifically. The setup I've found that seems to work best is to start the mission by flying straight down and then shoot the smartbomb half-way down to the ground.

6-5 (22:55/52:30)
Very tough mission (together with 4-1 and 6-1, the hardest segment). The enemy movements partly depend on your own movements, but also seem to be a bit random. Destroying two tanks with the third fireflash was e.g. not consistent. Because of the many different route options, it's very possible that a faster route exists, but this was at least the fastest I could find.
The thunderbolt destroyed a light beam robot on the other side of the wall. I found this to be very consistent. Funnily enough, I remember this to not be consistent on 'difficult' difficulty.
There is a tunnel under the level with some optional enemies and power-ups. One of the smartbombs in that tunnel can be collected on street-level thanks to how the hitboxes work though.
The recording quality is not the greatest, but I decided to settle for this. It's a challenging mission and the enemy movements were pretty favorable in this attempt. With all the action going on, it's also likely going to be difficult to get a much better recording even if more attempts are completed.

6-6 (23:36/54:01)
The intended way requires that you destroy some triggers while taking heavy enemy fire to access the rooms with the power generators. Fortunately, the thunderbolt is again abused to end the mission quickly. The setup is just to turn right when the mission begins and fire the thunderbolt. It's not very consistent for me though, so a single-segment run should plan for two thunderbolts in this mission.

6-8 (23:51/56:40)
There are three phases of the final boss. The first phase is to take out the turrets at the end of the four arms. The second phase is to shoot the four huge turrets at each corner of the energy shield blocking the access to the interior of the ship. The last phase is to destroy the ship's core, located in one of the arms. Each phase is unfortunately not activated before the previous phase has been cleared.

Final thoughts
The purpose of this speedrun was mainly to give the game some attention and document the routes and setups I've found. I would have preferred to do a single-segment speedrun (on 'difficult' - a single-segment 'extreme' speedrun does not look very feasible with the knowledge I have about this game), but the technical difficulties with recording this game through dosbox unfortunately don't allow that with my current setup. I would very much like to get back to this game if the conditions change though.

Credits
Lotblind provided some improvement ideas during the verification process, which helped bring the time down by several seconds.