1919 was a tough time.  With the war in Europe over, work in the armament and shipbuilding industries was drying up.  Glasgow  was a huge shipbuilding, armament and steel producer, primarily along the banks of the river Clyde, where thousands of warships were made.  The area had no small amount of labor unrest, some of it with socialist leanings, so much so that the neighborhood had acquired the name of Red Clydeside.  While striking for a 40 hour week, a battle took place at St. George's Square between the strikers and the Police, and while the details are sketchy, it appears to have been a Police riot, with the unarmed workers suffering the most.  

The British Government didn't want the workers getting out of hand.  The worker's revolution in Russia had the Government running scared, and they didn't take any chances.  The Scottish garrison was bottled up from fears they would go over to the workers side, and 10.000 British troops were brought in to keep the peace.  They brought their tanks with them, the Mark IV's of WW1, and some of them were probably built by the very men they were being used against.  Wm. Beardmore Company in Glasgow had built over 100 tanks during the war, along with fighter aircraft, and warships and their guns.  

Ten days later the strike was called off.  The workers didn't get their 40 hour week just yet, but they did get their 60 hour weeks reduced to 47 hours.  The Socialists hadn't given up on  Glasgow just yet, and their representatives even made it to Parliament, but their influence soon faded.  The image of tanks on the streets of Glasgow faded also, along with most heavy industry along the banks of the Clyde.

British Soldiers and tanks in Clydeside