Successfully complete the following missions with all gold medals to receive the corresponding medal:
 

D-Day mission: Army Distinguished Service Medal.
Storm In The Port mission: Army Commendation Medal
Needle In A Haystack mission: Soldiers Medal
Several Bridges Too Far mission: Dutch WWII Commemorative Cross
Rolling Thunder mission: Legion of Merit - Complete
The Horten's Nest mission: Distinguished Service Flying Cross

Gold Medal
Kill over 95% of the enemies and have over 75% health remaining at the end of a level to earn a gold medal.

Translation
Enter the options menu and turn on the subtitles. This will allow you to know what the Germans are saying.

A Chance Meeting: Falling Objects
When you enter the main U-boat facility and start to fight your way towards the docks, you will encounter several train cars. One of these cars has a mounted MG-44. Hit the switch on the other side of the car and it will roll until the gun is pointing through a doorway leading into an open area between the dockyard buildings. Use the gun to clear out the enemy. When done, proceed forward until you find more Nazis. One of them will shoot at you with another machine gun mounted on a sandbagged position. Behind that are a truck full of torpedoes and a crane that is holding several crates aloft. Use your Springfield sniper rifle and shoot the rope. The crates will fall on the truck, causing it to explode and kill the sniper on the crane and any nearby Nazis.

Clipping Their Wings: Hidden Chests
On the final mission where you are required to take pictures of the blueprints, there is a sleeping area. On the side of the room where you find the spy camera, check in between the bunks to find hidden chests. You will find canteens inside.

Derailed: Secret Passage
As you start the mission, go to your right and you will see a dirt road. Go slow because of a Nazi that is sitting down, waiting. You see something in the mountain. Go to the door but do not open it. Get ready to shoot -- there are three Nazis inside. Mow them down and grab the MG-42. Then, wipe out the remaining Nazis below.

Nijmegen Bridge: Destroy the AA Gun
At the end of the level, you will see a red barrel with a white rag sticking out of it that must be destroyed. Use the following trick instead of shooting the barrel or tossing a grenade to detonate it. Approach the side of the barrel with the rag. You should see the message "Press Action to ignite the rag" appear at the top of the screen. Do so, and you will hear the sound of Jimmy lighting a lighter and touching it to the rag. Immediately back away and wait. After a few seconds, the barrel will explode and the anti-aircraft gun will be destroyed without wasting any ammunition.

Nijmegen Bridge: Suicidal Nazi
When instructed climb up the ladder to top of bridge, do so. Note: Enable the "Invincibility" or "Bullet shield mode" codes to make this easier. When you reach the top of the ladder, a Nazi will be directly in front of you. He will aim his gun at you and begin to shake. Do not shoot him or any other Nazis. Wait for a moment, and he will stand up, grab his helmet, and jump off the top of the bridge screaming.

Omaha Beach: Saving Your Men
When you get out of the water, quickly get to an obstacle, then find the Higgins Boat where your lieutenant is located. Saving your men is difficult because cannot see very far. The will not wave at you unless you are close to them. Once you run up and down the beach a few times, you will hear them over the noise.

On Track: UFO
When you get outdoors next to Sturmgeist's train, look up and to the right. You will see a UFO flying in the air. If you look closely, it has the Nazi markings and colors.

On Track: Jimmy Patterson Poster
When you get to the entrance to the train station, stop and look on the left side of the entrance door. There will be a wanted poster of Jimmy Patterson with a picture. It even has a reward in German.

Operation Repunzel: Suicidal Nazi
There is a Nazi soldier practicing a speech in a hall where you find the map behind the painting. Instead of going around on the top, go downstairs and run up to him. He will automatically fall back and die without a single shot. The only downside is that you cannot get a gold star for this mission if this is done.

Operation Repunzel: Extra Health
After you kill all the waiters and the cook, look around and run to the bread. Jimmy will say that its yummy , and your health will rise more than a medical canteen.

Operation Repunzel: Speech Practice
You will encounter a man practicing his speech in a large hall inside the building where they are preparing to have a Nazi Rally. Instead of walking up to him, stay on the balcony and go across the walkway connecting the two sides of the room. He will see you and tell you to stop. He will then pick up the rocket launcher next to the podium and fire it at you. It will hit the walkway and blow it in half, forming a ramp from the ground floor to the upper level.

Operation Repunzel: Chandelier Kill
You can shoot the chandeliers that are around in some of the rooms of the Nazi building. They will kill anyone underneath, including you.

Rough Landing: Sniping Nazis
After Barnes blows up the tank that is inside a barn, you will get to a mill where you will find a sniper. Kill him, then get up to the mill. Snipe the large group of Nazis that will appear in the distance, as if they were following you.

Seaside Stowaway: Breach Wall To The Docks
You will see a red barrel with a white rag sticking out of it that must be destroyed. Use the following trick instead of shooting the barrel or tossing a grenade to detonate it. Approach the side of the barrel with the rag. You should see the message "Press Action to ignite the rag" appear at the top of the screen. Do so, and you will hear the sound of Jimmy lighting a lighter and touching it to the rag. Immediately back away and wait. After a few seconds, the barrel will explode and the dock wall will be breached without wasting any ammunition.

Yard By Yard: Civilian Backup
In one of the alleys, you will encounter an old women just sitting in her backyard. Next door to her lives a young man with glasses, lying on his lawn next to his shed. In his yard is a ladder propped up on a couple of boxes. Use this ladder as a ramp and walk across it. In this yard is a man with a helmet standing next to his shed. Do not shoot him. Walk up closely to him and he should have his arms raised, is clearly too old to be in the military. Stare at him until he puts his arms down and reaches into his shed window for a shotgun. Still, do not shoot him. By this time a Nazi soldier will storm into the man's yard. The old man will fire at him, killing him, and leave his yard looking for more Nazis. For good measure, stand as close to him as possible while he leaves his yard. He will give you a nudge to go while he covers you.

Yard By Yard: Create Hole
Shoot the dirt with a Panzerschreck and the man will sink down into a hole.

Your Finest Hour: Soldiers' Names
After your amphibious boat explodes, go to the shore where you will see a few dead men. Zoom in on there chest and you will see names such as Rus K (Risky) and others.