Sea denial is a military term describing attempts to deny an enemy's ability to use the sea (usually with naval blockades or port blockades) but at the same time making no attempt to control the sea itself. It is a far easier strategy to carry out than sea control because it requires the mere existence of a navy. The downside of sea denial is that fleets may become over-stretched as constant hit-and-run tactics

Hit-and-run tactics

Hit-and-run tactics is a tactical doctrine where the purpose of the combat involved is not to seize control of territory, but to inflict damage on a target and immediately exit the area to avoid the enemy's defense and/or retaliation.-History:...

 can erode unit strength, leaving them unready for direct action in main fleet combat.

During World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 and World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 Germany

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 engaged in a sea denial strategy with their U-boat

U-boat

U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...

s. They attempted to deny the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

' ability to transport supplies to Britain

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

but did not attempt to gain control of the sea so they could transport their own supplies over the ocean.