The U.S. Army D Ration—also known as the Logan Bar—was developed in 1937 by Captain Paul Logan of the U.S. Army Quartermaster Corps in partnership with Hershey Chocolate Corporation. Unlike a candy bar, the D Ration was designed as an emergency survival food that could withstand extreme heat, deliver approximately 600 calories per bar, and discourage soldiers from eating it unless absolutely necessary.

The original commercial formula remains proprietary, but surviving Army specifications and Hershey documentation reveal the primary ingredients and design requirements. This recipe recreates those characteristics as closely as possible using ingredients available to modern home cooks.

Recipe Information

Yield: 6 bars

Prep Time: 20 minutes

Cook Time: 15 minutes

Cooling Time: 2–3 hours

Difficulty: Moderate

Historical Design Requirements

The D Ration had four primary objectives:

• Approximately 600 calories per bar

• Stable in temperatures up to 120°F (49°C)

• Compact and durable enough for field use

• Taste only "slightly better than a boiled potato"

The final requirement was intentional—soldiers were not supposed to snack on them.

Ingredients

Chocolate Base

• 160 g unsweetened baking chocolate (100% cacao)

• 30 g food-grade cocoa butter

  • Make sure you buy food-grade, as cocoa butter is normally sold as a non-edible cosmetic.

Dry Ingredients

• 160 g granulated sugar

• 70 g nonfat dry milk powder

• 20 g oat flour

• ½ teaspoon vanilla powder (or ¼ teaspoon vanillin if available)

  • Vanillin is the historically accurate ingredient, but hard and often expensive to find today.

  • You can use liquid vanilla extract here, but it will add liquids and therefore may reduce the shelf life.

• Pinch of salt

• You can check out additional supplements for these bars here: How to Enhance Homemade D Ration Chocolate Bars

  • Mind you, it was not historically accurate to add these to the bars.

Optional (Historical Fortification)

• Vitamin B1 (thiamine) powder, food grade

Equipment

• Double boiler or heat-safe bowl over simmering water

• Mixing bowl

• Rubber spatula

• Kitchen scale

• Silicone bar molds or parchment-lined baking pan

• Heavy rolling pin or wooden block for compressing

Step 1 – Prepare the Dry Ingredients

In a large mixing bowl combine:

• Sugar

• Powdered milk

• Oat flour

• Salt

Whisk thoroughly until evenly blended.

Unlike modern chocolate bars, the oat flour is not a filler—it was intentionally included to increase calories while making the bar denser and more difficult to eat.

Step 2 – Melt the Chocolate

Using a double boiler, slowly melt:

• Unsweetened chocolate

• Cocoa butter

Avoid overheating.

The mixture should become smooth but remain fairly thick.

Step 3 – Combine Everything

Pour the melted chocolate into the dry mixture.

Add the vanilla.

Mix slowly using a sturdy spatula.

At first the mixture will seem far too dry.

Keep working it.

Eventually it becomes a stiff dough similar to modeling clay.

If absolutely necessary, add one teaspoon of warm water at a time, but use as little moisture as possible.

The original bars contained very little free moisture, which contributed to their long shelf life.

Step 4 – Compress

Transfer the mixture into molds or a parchment-lined pan.

Using another piece of parchment, compress the mixture with significant force.

Historically, Hershey used industrial presses to compact the bars.

Home cooks should compress as firmly as possible to recreate the dense texture.

Aim for a thickness of approximately ½ inch (13 mm).

Step 5 – Cool

Allow the bars to cool at room temperature for one hour.

Transfer to the refrigerator for an additional two hours.

Once fully hardened, remove and cut into bars measuring approximately:

• 4 inches long

• 2 inches wide

• ½ inch thick

Storage

Wrap each bar tightly in wax paper or parchment.

Store inside an airtight container.

Properly stored bars will last several months in a cool, dry location.

For maximum shelf life, vacuum sealing is recommended.

What to Expect

If you've never eaten a D Ration recreation before, don't expect a candy bar.

A proper recreation should be:

• Extremely dense

• Very hard

• Slightly bitter

• Dry

• Difficult to bite

• Slowly softens while being chewed

Many soldiers shaved pieces off with a knife or softened the bars in hot coffee before eating.

Estimated Nutrition (Per Bar)

• Calories: ~575–625

• Protein: 10–13 g

• Fat: 28–32 g

• Carbohydrates: 65–70 g

Historical Notes

The D Ration entered Army service in 1939 and remained in use throughout World War II before eventually being replaced by the Tropical Bar and other emergency rations.

Although often criticized by soldiers, the bars accomplished exactly what they were designed to do. Their dense texture prevented accidental overconsumption, their heat resistance made them practical in harsh climates, and their calorie density provided emergency nutrition when conventional food wasn't available.

One soldier famously joked that the bars were "hard enough to stop a bullet."

Modern Recreation vs. Historical Recreation

While this historical recipe stays as close as possible to documented WWII ingredients, many modern cooks prefer a version that's easier to prepare and more enjoyable to eat. The modern adaptation often incorporates honey, corn syrup, or additional chocolate to create a softer texture and sweeter flavor.

Which Version Should You Make?

Choose the Historical Recreation if you:

• Enjoy military history.

• Want an authentic museum-style experience.

• Are interested in survival food and historical rations.

• Want to understand what Allied soldiers actually carried during World War II.

Choose the Modern Recreation if you:

• Want something enjoyable to eat.

• Need an energy bar for hiking or camping.

• Prefer a softer texture and richer chocolate flavor.

• Want a recipe that's easier to make with common kitchen ingredients.

Both recipes pay tribute to one of the most iconic emergency rations in military history. The historical version offers a fascinating glimpse into wartime engineering and logistics, while the modern adaptation captures the spirit of the original in a form that's far more approachable for today's home cooks.

Shelf Life Note: The historical-style D Ration has the advantage for long-term storage because it uses very low-moisture ingredients and relies on cocoa butter, sugar, powdered milk, and oat flour rather than syrups or added water. Properly wrapped and stored in a cool, dry place, it may last several months to a year or more. The modern version is easier to eat and more enjoyable, but ingredients like honey, corn syrup, butter, or added water reduce its shelf life, making it better suited for short-term use, hiking, camping, or refrigerated storage.