XII Corps XII SS Corps Chronology of the liberation Logistics Operation Blackcock was an operation to clear German troops from the Roer Triangle, formed by the towns of Roermond and Sittard in the Netherlands and Heinsberg in Germany during the fighting on the Western Front in the Second World War.

The objective was to drive the German 15th Army back across the rivers Roer and Wurm and move the frontline further into Germany.

The next barrier was the River Roer, running from the German Eifel area through Heinsberg towards Roermond, where it joins the Maas.

Dutch South-Limburg was already liberated in September by the First United States Army, but the area above the Sittard–Geilenkirchen line was still in German hands.

These obstacles formed a triangular area, referred to as the Roermond Triangle, which protruded into the frontline like a bulge.

After four days of fighting, the Germans knew that the armoured division that was facing them relied heavily on the roads to manoeuvre their vehicles, especially due to poor winter conditions.

On 20 January, infantry and cavalry units of the Desert Rats launched a first attack on the (assumed) two German companies of the 2nd Battalion Fallschirmjäger Regiment Hübner in Sint Joost.

German paratroopers who were not killed only left the cellars under civilian cover, afraid that they would be shot by the victors.

The Desert Rats' losses in vehicles were rather light, with only 20 tanks knocked out by the enemy and a further 23 broken down due to mechanical problems.

Operation Veritable, by the First Canadian Army, was launched on the 8 February and was aimed at breaking through the German defences in the Klever Reichswald, some 60 km (37 mi) north of the Roer Triangle.

Operation Grenade, the southern part of the pincer movement, by the US Ninth Army was launched on 23 February.

General William Hood Simpson's US Ninth Army crossed the river Roer south of Heinsberg in the early hours of 23 February 1945.

A task force was formed by Ninth Army's XVI Corps which rushed towards Venlo to meet up with the British in the north.