Originally intended to be a sequel to Star Force, it was re-named Star Soldier due to a change in Hudson's relationship with Tecmo. It has received many upgraded remakes on various platforms. The series was hugely popular in Japan at the time, but never attracted the same popularity overseas. It was the contest game at Hudson's "2nd National TDK Famicom Caravan" in 1986 and remained popular and made frequent appearances at the Caravan while it was still being held; there was even a movie produced by Toho detailing the battle between the two top competitors, one of them being the famous Toshiyuki Takahashi.
The game features 16 stages; at the end of each stage is a boss called a "Star Brain" which must be destroyed; if the player cannot destroy a Star Brain within a certain period of time, they are returned to a midway point in the stage and must try again.
The player ship (called Caesar) has 4 levels of shot power. Level 1 is a basic shot; level 2 allows Caesar to move and shoot faster. Level 3 results in a change in the appearance of Caesar and a "rear-fire" ability. Level 4 grants Caesar a barrier which protects from enemy bullets and allows Caesar to shoot rapidly in 5 directions! Caesar also becomes temporarily invincible. The music changes when the player reaches level 3, and remains changed until the player loses this level of power. There are several other variations on this which are triggered by other conditions (I.E., losing the barrier downgrades Caesar to a three way shot) There are also various hidden power-ups throughout the game, often triggered by being able to shoot an object a certain number of times in a second. As another unusual feature, it is possible to hide under some pieces of the terrain: The player cannot be hit while doing this, but they cannot shoot either. This feature, while interesting, can lead to some degree of confusion.
- Melth: Resembling a red water beetle, these are the first enemy encountered. They approach in a zig-zagging pattern, but are very weak. Worth 100 points.
- Tyula: Spherical enemies that approach from the top, move in an arc, and exit again. 100 points.
- Riad: A tyula with a slightly different arc. 100 points.
- Jella: Disembodied flying wasp heads that sometimes shoot at the player. 100 points.
- Pring: Prings bounce downwards, much like their namesake the spring. They are of little threat. 100 points.
- Deida: Oddly shaped enemies that gyrate towards the player in an odd way. 100 points.
- Kalgo: Space snails the enter, shoot bullets wildly in all directions, and leave. 100 points.
- Atolis: Fast moving ships that are easily destroyed. 100 points.
- Bataf: Simple space butterflies that fly in various arcs. They sometimes will fly in lines, depending on where the player is. 100 points.
- Temis: Non-threatening wasps which enter from the sides. 100 points.
- Meeba: Amoebas that move slowly and come in groups. 100 points.
- Stellia: They enter from the top of the screen and fire at the player. 100 points.
- Reus: Saucer-type enemies that like to enter from the lower right or left corners, and then fly in a large arc in front of the player. 100 points.
- Rudan: Ships that gather in the center of the screen and then move off slowly. 100 points.
- Yaar: Fast moving dragonflies that fly in formation. 200 points.
- Prizun: Yellow ships which enter from the left side of the screen and sometimes shoot at the player. 200 points.
- Ruid: Another saucer-type, these turn in to sopplers when destroyed. 200 points.
- Kadeath: Yellow butterflies that zigzag fairly quickly. 200 points.
- Beeg: Disembodied flying bee heads that are fairly durable and shoot at the player. They can be a nuisance. 200 points.
- Solel: Blue ships that maneuver back and forth while advancing slowly and shooting at the player. Fairly durable. 200 points.
- Guha: They charge to the center of the screen, slow down, then charge away again. 200 points.
- Drak: Red shrimp that enter from the bottom of the screen slowly, then rapidly charge at the player. 300 points.
- Ache: Tadpoles that enter from the lower left and fly to the upper right at high speed. They often approach at difficult to hit angles. 300 points.
- Ri-de: Blue discs which appear in large numbers and shoot at the player. Relatively slow moving. 300 points.
- Pendo: Ships that fly in, break formation in various manners, then leave again. They are surprisingly threatening. 300 points.
- Slant: Extremely fast moving enemies which can enter from anywhere; they often simply try to collide with the player. 400 points.
- Patra: Enemies that try to attack the player from the side, on Caesar's blind spots. Quite menacing! 400 points.
- Soppler: Essentially a projectile, these are formed when ruids are destroyed; they are also fired by star brains. They are indestructible.
- Lazarus: A stone head which assembles itself after 4 pieces enter the screen from the corners. Worth 1000 points, but if the player can destroy one before it assembles they get an 80,000 point bonus!
- Jericho: A giant mechanical eye that shoots bullets rapidly in all directions. 1000 points.
- Star Brain: A star brain, regular sized. They shoot bullets and sopplers at the player. Worth 5000 points.
- Big Star Brain: A star brain... super sized! Similar to a regular star brain, but they're so big it's difficult to maneuver! The big star brain also has multiple parts: Each part is worth 5000 points.