The area in and around Colchester underwent huge changes during the twentieth century.
As an important garrison town in the 19th and early 20th centuries, Colchester played an important role in training troops following the outbreak of World War One in 1914. Many of those injured during the conflict were sent to Colchester to be cared for, with troops regularly arriving by train and being transported to the six Red Cross hospitals, the military hospital and Essex County Hospital. Outside the town, at least three night landing grounds were used by the Royal Flying Corps during the First World War, one of which later became the site of Wormingford airfield during the Second World War.
During World War Two Colchester was heavily defended, being encircled by the Eastern Command Line. Further anti-invasion defences were constructed along the coast including gun emplacements, searchlight batteries and observation posts. Several Second World War airfields were also established in the villages around Colchester, many of which were home to the USA Air Force.