25 June 1938 (United States)
The Wages and Hours (later Fair Labor Standards) Act is passed, banning child labor and setting the 40-hour work week. The Act went into effect in October 1940, and was upheld in the Supreme Court on 3 February 1941.
That's from
http://en.wikipedia.org/wiki/Timelin...ues_and_events
You can see how many times troops or Natl. Guardsmen were called out
May 1934 (United States)
Police attacked and fired upon striking Teamster truck drivers in Minneapolis who were demanding recognition of their union, wage increases, and shorter working hours. As violence escalated, Governor Olson went so far as to declare martial law in Minneapolis, deploying 4,000 National Guardsmen. The strike ended on August 21 when company owners finally accepted union demands.
20 April 1914 (United States)
The "Ludlow Massacre." In an attempt to persuade strikers at Colorado's Ludlow Mine Field to return to work, company "guards," engaged by John D. Rockefeller, Jr. and other mine operators and sworn into the State Militia just for the occasion, attacked a union tent camp with machine guns, then set it afire. Five men, two women and 12 children died as a result.[4][5]
Unions did violence too. But guards at Ford plants in the 30's carried Thompson sub-machine guns and used them regularly.