Ancient warfare
By the end of the wars in 221 BC, Qin had unified most of the states and occupied some lands south of the Yangtze River. The territories conquered by Qin served as the foundation of the Qin Empire.
Punic Wars
The Punic Wars were a series of three wars fought between Rome and the city of Carthage (a Phoenician descendant). They are known as the "Punic" Wars because Rome's name for Carthaginians was Punici (older Poeni, due to their Phoenician ancestry). They determined that the Romans would control the Mediterranean Sea and led to the eventual rise of the greater Roman Empire across Europe, Asia and Africa.
The First Punic War was primarily a naval war fought between 264 BC and 241 BC.
The Second Punic War is famous for Hannibal's crossing of the Alps and was fought between 218 BC and 202 BC.
The Third Punic War resulted in the destruction of Carthage and was fought between 149 BC and 146 BC.
Roman-Persian Wars
The Roman–Persian Wars were a series of conflicts between states of the Greco-Roman world and two successive Iranian empires: the Parthian and the Sassanid. Battles between the Parthian Empire and the Roman Republic began in 92 BC; wars began under the late Republic, and continued through the Roman and Sassanid empires. They were ended by the Arab Muslim invasions, which devastated the Sassanid and Byzantine East Roman empires shortly after the end of the last war between them.
Han–Xiongnu War
The Han–Xiongnu War, also known as the Sino-Xiongnu War, was a series of military battles fought between the Chinese Han empire and the Xiongnu confederated state located in modern day Mongolia from 133 BC to 89 AD. The final wars resulted in the final destruction of the Xiongnu as a political entity in Siberia. China would temporally enjoy peace on its northern frontier before new peoples such as the Xianbei took the role of the Xiongnu.
Roman-Germanic Wars
The Germanic Wars is a name given to a large series of military engagements between the Romans and various Germanic tribes between 113 BC and AD 596. The nature of these wars varied through time between Roman conquest, Germanic uprisings and later Germanic invasions in the Roman Empire that started in the late 2nd century. The series of conflicts which began in the 5th century, under the Western Roman Emperor Honorius, led (along with internal strife) to the ultimate downfall of the Western Roman Empire.

Unit types: 

See also: Ancient Mediterranean piracy
History of physical training and fitness
Horses in warfare
Women in warfare
Siege (Roman history)

References: 

Sources: Wu, Shu-hui (2013). "Debates and Decision-Making: The Battle of the Altai Mountains (Jinweishan 金微山) in AD 91". Debating War in Chinese History. Leiden: Brill. ISBN 978-90-04-22372-1.

Literature: Anglim, Simon, and Phyllis G. Jestice. Fighting Techniques of the Ancient World (3000 B.C. to 500 A.D.): Equipment, Combat Skills, and Tactics. Dunne Books: 2003. ISBN 0-312-30932-5.
Adams, William Y. (2013). Qasr Ibrim: The Ballana Phase. Egypt Exploration Society. ISBN 978-0856982163.
Bradford, Alfred S. With Arrow, Sword, and Spear: A History of Warfare in the Ancient World. Praeger Publishing: 2001. ISBN 0-275-95259-2.
Connolly, Peter. Greece and Rome at War. Greenhill Books: 1998. ISBN 1-85367-303-X.
Gabriel, Richard A. The Great Armies of Antiquity. Praeger Publishing: 2002. ISBN 0-275-97809-5
Gichon, Mordechai, and Chaim Herzog. Battles of the Bible. Greenhill Books: 2002. ISBN 1-85367-477-X.
Goldsworthy, Adrian. The Complete Roman Army. Thames & Hudson: 2003. ISBN 0-500-05124-0.
Keegan, John. A History of Warfare. Vintage: 1993. ISBN 0-679-73082-6.
Kern, Paul Bentley. Ancient Siege Warfare. Indiana University Press: 1999. ISBN 0-253-33546-9.
Leblanc, Steven A. Prehistoric Warfare in the American Southwest. University of Utah Press: 1999. ISBN 0-87480-581-3.
Mayor, Adrienne. Greek Fire, Poison Arrows & Scorpion Bombs: Biological and Chemical Warfare in the Ancient World. Overlook Press: 2003. ISBN 1-58567-348-X.
Peers, Chris J. Ancient Chinese Armies 1500–200 BC. Osprey Publishing: 1990. ISBN 0-85045-942-7.
Peers, Chris J., and Michael Perry. Imperial Chinese Armies : 200 BC–589 AD. Osprey Publishing: 1995. ISBN 1-85532-514-4.
Sabin, Philip. Lost Battles: Reconstructing The Great Clashes of the Ancient World. Hambledon Continuum: 2007. ISBN 1-84725-187-0.
Van Creveld, Martin. "Technology and War: From 2000 B.C. to the Present". Free Press: 1991. ISBN 0-02-933153-6.
Warry, John Gibson, and John Warry. Warfare in the Classical World: An Illustrated Encyclopedia of Weapons, Warriors and Warfare in the Ancient Civilisations of Greece and Rome. University of Oklahoma Press: 1999.

External links: Evolution of Sling Weapons
War in ancient Greece: a bibliography