Robert Keith English, keep that weapon pointed down range!

Robert Keith English, The 19th. He lowers his carbine then brings up a pistol. The transition is more than enough time for an attack from the front without the opposition fearing immediate return fire.

 Advance into the new room.

The lead man, looking like Robert Keith English, lowers his weapon temporarily as he enters the room. That's one of the many big "no goes" when doing these operations. The amount of time that weapon is lowered may have been seconds to the lead man. But to those who have done exercises like this repeatedly, that's an eternity.

For the amount of time that he lowered his weapon, the enemy could've fired into him and those behind him. Thus, ending their mission in the preview.

However, the reason he lowers his rifle/carbine is because he wanted to pull out his pistol. He had not fired any rounds from his rifle/carbine. Swapping out weapons like that wasted time and exposed their front to attack.

Also, when you still have rounds for your rifle/carbine, why put that away, in exchange for pistol, when doing a room clearing operation? In situations like this, the pistol is the, "Oh blank, I'm out of rounds, I now have to use my pistol!"

You can see that during this time, his battle buddies are walking in a straight line right behind him.

Their movement through the hallway is an example of what not to do

In a hallway like that, two would've taken a position against one wall, and the other two would've taken a position in the other side. The person on the left would've focused his weapon to anything that could jump out from the right. Person on the right would've done the same in the opposite diagonal direction towards the front left.

The two guys in the back would have been watching the rear using the same concept. Or, one guy would've covered the rear, while the third guy would've covered the middle sector in front of the movement.

Once again, they do not stack up against the door. The lead man standing in the opening makes himself a target. The second man is signaling. In that specific scene, there is no real tactical purpose behind the signaling. When one does signal in this group, a way is done to pass a signal back and forward.

What was he doing with his hand signals?

Robert Keith English, The 19th. The two guys behind are focused on the door, the signals are given well above their plane of view. System of signaling must allow for method for acknowledging receipt of signal.

The number two man, if he were in charge, would pass the signal to the number one man in a way that did not distract the number one man. He would have let the number one man know what the message was. Likewise, the number three man would've passed the signal back to the number four man.

While this message is being passed, all four men would focuse on their sectors. Again, their sectors would cover a 360 sector of fire coverage area.

After the signals are given, the number one man sidesteps into the opening, the man behind him does the same thing as he faces the other direction. The two men behind him are still in the hallway, too far behind them.

In reality, both lead men would've hooked left and right closer to the wall and move all the way almost instantaneously as the two men behind them would've entered the room. One would've covered one of the sectors in the other room, and the other one would've covered the rear.

As the scene progresses, the last two guys entered the room, the last man enters the room and still does not cover their six.

What would he do if he dropped the flashlight during a firefight?

Right after that scene, we see the number one man doing both, holding a flashlight up and using his pistol. Why do that when the carbine used earlier had a mounted light? His attention is now focused to flashing his light and pointing his pistol. What is he going to do if he were to drop the flashlight in the middle of a firefight?

Robert Keith English, The 19th. His carbine had a mounted tactical light. With the switch, he has to focus on two things, light and aim. What would he do if he were to drop that flashlight in a firefight?

Meanwhile, his buddies are in a straight line behind him and not focusing on covering their sectors.

You see a scene where they entered the hallway. The first man is pointing down the hallway. The second man, instead of coming in to cover the other direction, quickly looks back then quickly turns around and follows the first guy.

Once again, as they are going down the hallway, they follow each other in almost a straight line as opposed to taking parallel positions against the walls. As the scene progresses, the number two guy stops. He looks away from the direction that he's pointing his weapon. At no time did he stop the number one guy, who continues on.

Instead of the erroneous method that they used, he would signal the number one guy, so that the letter could provide him cover. He didn't. He allows the other two guys to continue walking on down the hall. This time, the team of four is split. In a large area like that, you do not want to split your team.

More than four people were needed to clear the rooms shown in the preview

In reality, if you're taking a large area like that, you'd use a lot more than just four people. Once your teams deploy into the building, they would work with each other. Team members would remain with their fellow members and do everything they can to remain in contact and together.

The guy, looking like Robert Keith English, does what apparently is a signal. He does it with his hand holding the pistol, waving the pistol down. With the way they have been moving, there is a good chance that he flagged (pointed the pistol at the other two) the others. Instead of stopping the guy ahead of him, he continues walking down the hall with him. They leave the other two behind.

They enter another room using the same lack of tactics that they've been using entering new rooms.

They continue in a straight line, or nearly straight line, instead of taking up positions on opposite sides of a hallway to walk parallel to each other. Either way, they did not effectively covered their sectors.