When you board the dropship, you will find Admiral Anderson there to greet you, along with another soldier, Major Coats (this is the soldier who was featured in the very first teaser trailer of Mass Effect 3.) When Anderson greets you, you will have the opportunity to use a Paragon interrupt, which will make the proceedings a little more personal. From here, you can question him on the status of Earth’s forces, or you can simply push on to the next subject, either congratulating Anderson on his heroism or remaining impassive and down-to-business.
After your conversation, the dropship will land in the Alliance’s London base. It’s a pretty small operation, with only a few soldiers and APCs having survived the Reaper’s attacks thus far, but it will be your best shot at organizing an offensive. It will also give you the chance to take a break from all of the fighting that has consumed this level so far. You will be able to freely run around the base and speak with your squad-mates for one last conversation. You can also speak with a few of the soldiers, and even a few familiar faces from earlier in the game who unfortunately won’t be fighting side by side with you in the upcoming battles.
First things first, head to the left between the two APCs to find a Datapad sitting in the debris. Pick it up and read it. Now, set out to find the different members of your squad. Kaiden can be found at the corner, prepping for the battle with a few other soldiers. You can ask him about his squad of Biotics and reassure him of your friendship. If Kaiden didn’t live, you will find Ashley here instead. You can ask her about the upcoming mission and the soldiers who she is assigned to lead into battle. If you decided to pursue a relationship with either of them, this last conversation will be a little more personal and tragic.
Head into the building at the back of the area and to the right. Here, you will find a man operating a communications station of some sort. You will be able to communicated with your allies from Mass Effect 2, including Jacob, Jack, and Samara (if they are still alive) using this terminal, so wish each of them luck before heading outside and up the pile of rubble that functions as a ramp to the next level. Up on the second floor, you will find Garrus conversing with the other turian soldiers. He will be in a debate with Wreav via radio, telling him to play nice with the geth and share supplies. You can speak with him and address the many years that you’ve spent as friends (and potentially lovers) aboard the Normandy. Promise him a drink when this is all over, and tell him that if you die, you will watch over him from the afterlife to gain Paragon points, or keep it informal to gain Renegade points. You can also address your relationship with Garrus here, if you chose to romance him.
You will find Victus leaning against the wall on the left side of this building. Speaking with him will get a few lines of consolation about the condition of Earth. Head out of the opening next to Victus to continue on your tour of the Alliance base. You will come to a bridge that crosses to the other side of the base. As you cross the bridge, the soldiers will yell and a group of enemies will approach the base. A vehicle will be destroyed as a wave of Husks rushes the Alliance compound. Man the turret sitting at the edge of the bridge and take aim at the Husks. Be sure to target those who have already begun scaling the wall first. They will first come from the left side, then the right, and the waves will continue to alternate sides each time they begin. There will be around four to five waves, total.
When the Husks are all dead, continue on across the bridge. As you approach the entrance to the next room, examine the sickbay area to find more Med Kits and another Datapad in the small hall to the right. Continue into the next room. You will find Liara here. Speak with her and reassure her that you will make it through this conflict unscathed. If you romanced Liara, she will offer you a gift. Accept it, and she will touch you, granting you access to her mind for one last kiss. Keep following the path and you will be led up above the buildings, where you will find Wreav delivering a speech to a group of eager krogan waiting below. You can speak with him here to get pumped up for the battle ahead. When you are done talking with him, head up the slope and through the door.
Follow the path to the right to reach the planning room, where Anderson and Coats will have already set up shop. A group of geth soldiers will be mingling with the others to the right, and you can speak with the Geth Prime to learn that synthetic reinforcements are on the way. Pick up another Med Kit from the fallen pillar sitting across from the Geth Prime, and then speak with EDI, who will be standing near Anderson. She will be afraid, a feeling that is new and confusing to a VI, and you can reassure her. After this, speak with Anderson to formulate the plan of attack. Apparently, only 25% of Hammer squad, the group of soldiers who were supposed to aid your attack on the Citadel Beam, remains. The rest have all been wiped out. Still, it’s now or never, and the Admiral will defer to you to give a rousing speech to the men and women before they rush out into the fray. You can use Paragon options to keep the speech focused on the friendships and the love that has been created by the impending approach of the Reapers. Then, at the end, you will encourage them to think of these bonds and gain strength from them. Alternately, you can use the Renegade options to focus on the destruction that the Reapers have caused, and the desire for revenge that burns deep in the hearts of every race right now. You can even mix and match options for a weirdly disjointed speech to the troops. When you are done, you will be packed into a vehicle and ushered out to the next area.