--- a/API/Objects/Requirement/RequiresAtLeastNUnitsRequirement.cs	Sun May 01 13:56:20 2011 +0000
+++ b/API/Objects/Requirement/RequiresAtLeastNUnitsRequirement.cs	Sun May 01 14:23:51 2011 +0000
@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using IBBoard.WarFoundry.API.Objects;
+using System.Text;
 
 namespace IBBoard.WarFoundry.API.Objects.Requirement
 {
@@ -180,8 +181,28 @@
 
 		protected override string GetValidationFailedMessage (Army army)
 		{
-			string message = "";
-			return message;
+			StringBuilder sb = new StringBuilder();
+			sb.Append("Army must contain: ");
+			sb.Append(String.Join("; ", GetFailedRequirements(army).ToArray()));
+			sb.Append(".");
+			return sb.ToString();
+		}
+
+		private List<string> GetFailedRequirements(Army army)
+		{
+			List<string> failures = new List<string>();
+
+			foreach (UnitCountRequirementData requirement in requiredTypes)
+			{
+				int unitCount = army.GetUnitTypeCount(requirement.UnitType);
+
+				if (unitCount < requirement.Count)
+				{
+					failures.Add(requirement.Count + " × " + requirement.UnitType.Name + " (have " + unitCount + ")");
+				}
+			}
+
+			return failures;
 		}
 	}
 }