Military activities dominated the first half of the century. During the First World War (1914-18) German U-boats were active in the North Channel and Luce Bay. The graves of sailors drowned in the sinking of the Main in 1917 and the Rio Verde in 1918 are to be seen in Kirkmaiden kirkyard.

Other vessels also were torpedoed or sunk by gunfire. To counteract, the Royal Navy Air Service (RNAS) in 1915 established an airship base at East Freugh.

RAF West Freugh was opened in 1937 as an Armament Training Camp. During the Second World War (1939-45) it expanded to include training facilities for Observers, Navigators, and Bomb Aimers. It also served as a base for the Bombing Trials Unit. Operations continued after the end of the war. West Freugh today serves as a weapons trial and satellite tracking station.

The Second World War also saw the temporary and unsuccessful establishment of an emergency landing ground and supply dump on the west side of the Sandhead-Drummore Road, just south of Logan Toll. An air-sea rescue unit operated from the large, ugly shed still standing at the foot of Stair Street, Drummore. 'Land girls' were based in a hostel at Drummore, while others stayed on the farms where they worked. Many children from the Glasgow area were billeted as evacuees with local families.

The war years saw the conversion to arable of much land formerly fallow. In the second half of the century death duties on estates brought about the sale of many farms to their former tenants. The ever-increasing use of machinery reduced the number of farm workers and led to the consolidation of larger farm units. The growth in the number of cattle made it necessary to have larger fields for grazing and the growth of fodder.

Continued depopulation forced the closure of village schools, shops, churches and post-offices. Local landmarks such as Logan Tollhouse and Drummore Castle were destroyed. As against this, the ever-increasing use of the car made journeys to and from other parts of the United Kingdom easier for everyone. Tourism in general became more important. Caravan sites opened in many parts of the area. Visitors sometimes became permanent residents, thus going some way to solve the problem of depopulation.