List of military engagements of World War I encompasses land, naval, and air engagements as well as campaigns, operations, defensive lines and sieges. Campaigns generally refer to broader strategic operations conducted over a large bit of territory and over a long period of time. Battles generally refer to short periods of intense combat localised to a specific area and over a specific period of time. However, use of the terms in naming such events is not consistent. For example, the First Battle of the Atlantic was more or less an entire theatre of war, and the so-called battle lasted for the duration of the entire war.