Trekkie combat, Star Trek combat, and Real combat
Scenario 1: Rescue prisoners
Mission requirements: 16 prisoners are being held in a Romulan prison complex. They are spies who were caught after breaking into a highly classified research facility. Starfleet Command wants them back, to find out what they saw.
Intel report: The prison complex is a standard walled facility with guard towers, and there are (damping fields, energy fields, jamming fields, transport interdictor fields, low-level shields, duranium walls, funny ore in the surrounding hills, whatever) that prevents direct transport in or out. Sensor readings of the complex itself are obscured, thus rendering more detailed analysis impossible.
Equipment and Manpower: The USS Defiant and one commando team.
Precedents: The use of small insertion teams behind enemy lines with no advance reconaissance is not unprecedented in Star Trek. See "Chain of Command".
Note: one could replace the Romulans in this scenario with pretty much anybody, from the Klingons to the Cardassians, the Dominion, the Breen, and yes, the Empire.
Trekkie fantasy
The USS Defiant crosses the Neutral Zone and enters the star system under cloak. It beams a landing party of 20 heavily armed Starfleet Marines to the surface, commanded by a rip-snortin' lieutenant with 22-inch biceps. These men are equipped with portable forcefield generators, portable transporter units, mortars, photon grenades, bazookas, phaser rifles, personal cloaking devices, and heavy body armour (in other words, every toy ever seen in the history of Star Trek ground combat, along with a few figments of Trekkie imagination).
The team immediately uses their tricorders to scout out the Romulan base, now that they are close enough to burn through the jamming. They locate the prisoners in the northeast block. They take advantage of the element of surprise, and demolish half of the eastern wall with a single phaser blast. When the Romulans react, they incapacitate every Romulan in the entire complex with phasers set on wide-beam stun. They swiftly move into the remains of the northeast block, locate the prisoners, and then calmly escort them out of the shattered complex before any of the stunned guards can regain consciousness. They beam up to the Defiant, which slips away. Mission accomplished, zero Starfleet casualties.
Likely DS9 writers' solution
The USS Defiant crosses the Neutral Zone and enters the star system under cloak, after having a chance nose-to-nose encounter with a Romulan warbird which nearly detects them, but is suddenly called away, thus causing everyone on the bridge to breathe a sigh of relief (no one stops to wonder what the odds are that two ships would just happen to pass within a few kilometres of each other in the staggering vastness of interstellar space).
When it arrives, it beams down an eclectic complement of mixed personnel who have never worked together before. Naturally, the entire bridge crew of DS9 is there. Several nondescript people in gray shirts mill about in the background. There's a nervous guy, a smart technical guy, an angry guy who's itching for combat, several people who don't even merit description, and a woman who reminds Ezri Dax of one of her previous hosts. This motley collection of mixed, unfamiliar personnel with vastly different specializations is, of course, expected to function smoothly as a team, and Captain Sisko gives an inspiring speech. One of the other DS9 bridge personnel provides encouragement to the nervous guy.
They appear in the forest very far from the base so as to provide an excuse for lots of walking and talking time, and they begin to move slowly toward it. Ezri tries to scan the base with her tricorder, but she still can't pick anything up. Sisko orders her to "keep working on it", and the nondescript technical guy helps out. She jabbers nervously at him, and he tries to buoy her spirits in that calm, comforting tone of voice that we men always use when we really, really want to get into a woman's pants. The team makes camp for some reason, thus giving everyone lots of time to get acquainted. The angry guy and the nervous guy get the most character development and it is revealed that they don't get along, thus leading us to wonder which one is destined to die.
Ezri and her horny friend figure out how to "recalibrate the tricorder to scan in the upper theta band", thus miraculously giving them a complete picture of the complex and a location fix on the prisoners. The tricorder also locates a subterranean tunnel leading into the complex (naturally). One of the nondescripts grumbles that he hates tunnels. They enter the complex through the tunnel (which leads into an air vent), find and release the prisoners, and start to make their way back, when BAM! One of the nondescripts is hit in the back and killed by a Romulan disruptor blast. Let's get ready to rumble!
There are a lot of metallic packing crates laying around in the corridors for some reason, and the battle immediately turns into a game of "duck behind crate, pop up, shoot, duck back down" on both sides. The nervous guy is cowering behind a crate, and the angry guy is recklessly blasting at everything in sight. More and more Romulans show up, and the Feds begin to beat a hasty retreat to the tunnel. In the running firesight, one or two more nondescripts die. They find the tunnel and start piling in, while the angry guy and the nervous guy fight a holding action. Just as the Sisko climbs into the tunnel opening, a Romulan fires a disruptor blast at the nervous guy, but the angry guy jumps in front of him and takes the hit. The nervous guy is stunned for a moment, and then becomes imbued with an otherworldly rage, mowing down Romulans left, right and centre. He shouts "you go on, sir! I'll hold them!"
Sisko gives him a macho nod, and climbs into the tunnel. As the team escapes, we see slow-motion shots of the nervous guy bravely holding the line while standing over the body of his dead comrade, until he is finally overwhelmed and takes multiple hits. He goes down fighting.
We never even see how the team evades the inevitable pursuit in the forest. We cut immediately to Captain Sisko's office on DS9, where Doctor Bashir is handing him a PADD containing the mission logs. He mentions that the families of the dead men have not yet been contacted, and that the spies are in their debriefings. Sisko gets up, walks deliberately to the window, and slowly intones a monologue about how he hopes it was worth it. Yes, he hopes to God that it was worth it. Such a waste ... yadda yadda yadda. Momentous music. Fadeout.
Realistic Mission
The USS Defiant crosses the Neutral Zone and enters the system under cloak. It beams down a team of 20 men along with an equipment crate to the surface. Each man hits the ground running, but he can't see any of the other team members! The Romulans had a transport scattering field in place (which anyone with a tractor beam could make), and the men have been been scattered all over Hell's half acre. One by one, they meet up at a pre-arranged rallying point. 2 men are missing after three hours and presumed dead, probably from being randomly transported into a solid object. One man has a broken leg from materializing 15 feet above the ground. They put his leg in a splint, and they have no idea where the equipment crate is, so they have to work without it.
They spread out and move swiftly through the forest, eventually reaching an elevated position. One of them uses a pair of simple optical binoculars to get a good look at the camp from a distance, since tricorder scans would give away their presence and location. Intel said that the prisoners were in the northeast block, but they can't see inside. The men set up a perimeter and wait, in the hopes that the Romulans will eventually move the prisoners and they'll be able to figure out roughly where they are.
After three days, they've identified all of the Romulan guards' patrol routes but they haven't seen the prisoners they're looking for. They've seen prisoners out in the open, but none of them were human. The mission cutoff date is approaching, and the mission commander makes the call to infiltrate the base.
They move in close, and four men with sniper rifles eliminate the patrols in one area. They shift targets, and take down the guards in the northeast tower. The remaining 13 men hook their way up the wall and into the tower, and they enter the base. They're on a clock, because the Romulans will quickly figure out that something is up when the patrols or the tower guards don't report in at the next regular interval. They kill one guard inside, and then they fan out and check every cell in the block. However, they come up empty. The alarm sounds, and the guards converge on their position. In the ensuing firefight, 8 of the men are killed, and the remaining 5 are captured.
The sensor jamming field around the base suddenly vanishes. The snipers in the forest realize what this means: the Romulans have turned it off so that they can use their own sensors to get a clear picture of the forest. In other words, they've been made. They run like hell, break radio silence, and request emergency evac from Defiant. However, while the jamming field is down, there's still some sort of (damping field, energy field, interdictor field, funny ore in the surrounding hills, whatever) which prevents transport. All four snipers are hunted down. Two are killed, two are captured.
The lone mission survivor is the man whose leg was broken, and who was left at the rallying point. During the debriefing, it is learned that Intel screwed up. The prisoners were being held at a completely different prison complex, in a different star system. The Romulan ambassador angrily denounces the Federation's armed incursion into Romulan territory, and the Federation ambassador denies any official knowledge of the incident. The captured mission operatives are put on trial and publicly executed. Life's a bitch.