in earlier wars without as much human attention. The Germans used gas-filled shells at the Battle of Bolimov on January 3, 1915. These were not lethal, however. In April 1915, the Germans developed a chlorine gas that was highly lethal, and used it to moderate effect at the Second Battle of Ypres. Gas masks were invented in matter of weeks, and poison gas proved ineffective at winning battles. It was made illegal by all nations in the 1920s. World War II gave rise to even more technology. The worth of the aircraft carrier was proved in the battles between the United States and Japan like the Battle of Midway. Radar was independently invented by the Allies and Axis powers. It used radio waves to detect objects. Molotov cocktails were invented by General Franco in the Spanish Civil War, directing the Nationalists to use them against Soviet tanks in the assault on Toledo. The atomic bomb was developed by the Manhattan Project and dropped on Hiroshima and Nagasaki in 1945, quickly ending World War II. During the Cold War, the main powers engaged in a Nuclear arms race. In the space race, both nations attempted to launch human beings into space to the moon. Other technological advances centered on intelligence (like the spy satellite) and missiles (ballistic missiles, cruise missiles). Nuclear submarine, invented in 1955. This meant submarines no longer had to surface as often, and could run more quietly. They evolved into becoming underwater missile platforms. Periods of military history Ancient warfare Much of what we know of ancient history is the history of militaries: their conquests, their movements, and their technological innovations. There are many reasons for this. Kingdoms and empires, the central units of control in the ancient world, could only be maintained through military force. Due to limited agricultural ability, there were relatively few areas that could support large communities, so fighting was common. Weapons and armor, designed to be sturdy, tended to last longer than other artifacts, and thus a great deal of surviving artifacts recovered tend to fall in this category as they are more likely to survive. Weapons and armor were also mass-produced to a scale that makes them quite plentiful throughout history, and thus more likely to be found in archaeological digs. Such items were also considered signs of prosperity or virtue, and thus were likely to be placed in tombs and monuments