While the overall literary technique in Animal Farm is satire, Chapter 4 shows two very common techniques: suspense, and false climax. Suspense is shown in the scenes where the farmers march on the Animal Farm, looking to battle the animals and take the farm back. Although it is clear that Snowball has prepared for this event, the farmers are human and Jones has a gun; despite Snowball's preparations, the animals are, after all, just animals. However, they are more ready for the farmers than expected, and run them off. It is telling that Napoleon's name is not mentioned at all during this battle; he later takes credit for Snowball's military prowess.
The technique of false climax comes under several names, but is most often seen as the "calm before the storm" and is seen when there is a hopeful moment before a tragedy. Here, the routing of the farmers is a major victory for the animals, and gives them reason to celebrate:
The flag was run up and Beasts of England was sung a number of times, then the sheep who had been killed was given a solemn funeral, a hawthorn bush being planted on her grave. At the graveside Snowball made a little speech, emphasising the need for all animals to be ready to die for Animal Farm if need be.
(Orwell, Animal Farm, msxnet.org)
However, this victory is followed by several setbacks, some of which are created by Napoleon himself. By the end of the story, this decisive victory is all-but forgotten, replaced with the mindless worship of Napoleon; instead of being a symbol of animal bravery and victory over humanity, the Battle of the Cowshed comes to represent the last time the animals are all united with each other for the common good. Soon after, Napoleon expels Snowball and starts his movement towards dictatorship.