The Secret Army (Armée Secrète/Geheim Leger) was the largest group within the Belgian Resistance during WW2. It provided valuable intel to the allies, helped crashed pilots, eliminated collaborators, acts of sabotages and other things.
At his height it had 54,000 members across Belgium. Around 4,000 members of the Secret Army were killed during the occupation.
The Secret Army enjoyed the closest (but tense as neither group trusted the other) relations with the Belgian government in exile in London of any large resistance movement. The majority of the aid sent to the resistance in occupied Belgium was delivered to this group.
Shortly after D-Day in June 1944, the Secret Army was ordered to begin sabotaging railway and communications networks. Together with other groups including the Front de l'Indépendance and Witte Brigade, Secret Army personnel played an important role in the capture of the Port of Antwerp in September 1944 before the arrival of Canadian troops, preventing the Germans from destroying the installation as they prepared to retreat.
This patch is also the insigna used by the The Independent Belgian Brigade which was a Belgian and Luxembourg military unit in the Free Belgian forces during World War II, commonly known as the Piron Brigade (Brigade Piron) after its commanding officer Jean-Baptiste Piron. It saw action in the Battle of Normandy, the Liberation of Belgium, and fighting in the Netherlands over 1944-1945.
The D-Day landings took place on 6 June 1944 without Brigade Piron, to the great disappointment of its 2,200 men but the British preferred to reserve them for the liberation of Belgium. (This policy was applied to all of the smaller national military contingents, which were expected to form the basis of post-war armies and for whom it would have been difficult to find replacements for casualties.) Piron lobbied the Belgian government in exile, which requested the British Government to send the Belgian troops to the front, to reverse the declining morale of those troops.
During their advance through Belgium, the Belgian troops were sometimes mistaken for French Canadians, since local people did not expect that their liberators would be fellow Belgians. Brigade Piron liberated other Belgian towns and cities before reaching the Netherlands border on 22 September. Its campaign in the Netherlands lasted until 17 November, when it was relieved from the front and moved into reserve in Leuven. In the small Dutch border town of Thorn, a bridge has been named in honour of its liberation on 25 September 1944.
Brigade Piron returned to the Netherlands between 11 April 1945 and June 1945. The last casualty of the Brigade occurred on 27 April 1945. The next day, the Brigade was thrown into battle once again around Nijmegen. On that day an armistice was implemented in the Netherlands. The Brigade entered Germany in May before being disbanded in December. Its tradition was however preserved in the Bevrijding (Liberation) battalion of the 5th Regiment of the Line.
All sides of the triangle are 80mm (3.15'')