The story of the squadrons follows the great epics of Bomber Command.

When war broke out in Europe in 1939, Royal Australian Air Force (RAAF) aircrews were among the first Australians to head overseas to Britain's aid. Between 1939 and 1945, they flew in both Australian and British squadrons with the Royal Air Force (RAF) in Coastal, Bomber and Fighter Commands.
Identified as the Ceylon squadron, 102 Squadron was active from the second day of the Second World War, dropping leaflets in the night from 4 to 5 September 1939 over Germany. When the next leaflet raid was made - again on the Ruhr - four nights later, two of the six crews involved failed to return. Subsequently it was learned that one of these crews had forced - landed in then neutral Belgium and had been interned, and that the other had forced - landed in Germany and been made prisoners of war.
From 1 September till 10 October 1940 the squadron was loaned to RAF Coastal Command and spent six weeks carrying out convoy escort duties from RAF Prestwick, before resuming bomber raids. Operations Record Books seen at the Public Record Office in Kew show that 2 Whitley Mk.Vs flew out of Topcliffe on 27 November 1940 to bomb "docks and shipping" at Le Havre. One of these planes "was not heard from after takeoff" but the other returned safely having dropped its 2x500lb and 6x250 lb bombs successfully. By February 1942 the Whitleys were replaced by the Handley Page Halifax. The squadron continued for the next thirty-six months to fly night sorties (including the thousand bomber raids) over Germany. In 1944 the squadron attacked rail targets in France in preparation for the invasion.

In 1942 No 102 Squadron re-equipped with Halifaxes and continued with aircraft of this type for the rest of the European war. It took part in each of the three historic 1,000-bomber raids in May/June 1942, and, later, in the battles of the Ruhr, Hamburg, and Berlin. It was well to the fore in the pre-invasion attacks on railway communications in Northern France and on the eve of D-Day sent 26 aircraft - the largest number it had yet dispatched - to bomb an enemy gun battery on the coast of Normandy. In September/October 1944, it undertook the transportation of petrol to Belgium for the Second Army and in just over one week carried 134,250 gallons without mishap. In the great day and night 1,000 - bomber attacks on Duisburg in the closing stages of the war some of its crews made two round trips within twenty-four hours.