Those soldiers in THE FINAL COUNTDOWN were pussies! They only went back 39 years, the dudes (and chick) in HEAVEN'S SOLDIERS go back 433 years! Sadly, more years doesn't equal better movie though.
North Korea makes a nuclear warhead and agrees to hand it over to America. A North Korean officer is unhappy with this decision, so with a small group of dedicated soldiers he steals it. Hot on his tail is a group of South Korean commandos. Right when they catch up and start fighting a comet flies overhead and instantly transports them back to the year 1572. Why not?
Now in a hostile time period the two groups combine forces to figure out what the fuck is going on. The soldiers encounter a young man named Yi Sun-sin (according to Wikipedia he was a great military commander who lead Korean forces to victory against the invading Japanese military 23 times!!! Well, goddamn that's pretty impressive!). When the future soldiers meet him though his just a young aimless dude, but then they find out his identity and vow to protect him no matter what.
That's an OK story, but still I didn't like the movie. The entire thing is just too predictable and boring. Even worse is it looks like shit. I've seen TV shows with better CGI and special effects. The script is already weak to begin with and then the cheesy FX just took me completely out of the story. Skip it.