now-missing Fordson. Around 1930, the United conglomerate collapsed. The reasons that various authors have given have been disagreements between its investors, the onset of the Great Depression, and the fact that Ford Motor Company Ltd of England, which was continuing the Fordson line independently of the U.S. Ford company, began exporting new Fordsons to America. The United tractor became the Allis-Chalmers Model U. 1930s The 1930s were a pivotal decade. Despite the Great Depression, Allis-Chalmers succeeded as demand for its machinery continued. In 1931, it acquired Advance-Rumely of La Porte, Indiana, mostly because Merritt wanted the company's network of 24 branch houses and about 2,500 dealers, which would greatly increase Allis-Chalmers's marketing and sales power in the farm equipment business. Also in 1931, the corporation's electrical equipment business expanded via acquisition when Brown, Boveri & Cie, in a financial pinch because of the Depression, sold its U.S. electrical operations to Allis-Chalmers. After 1931 Allis-Chalmers was the licensee for U.S. sales of European products of Brown, Boveri & Cie. In 1932, Allis-Chalmers collaborated with Firestone to introduce pneumatic rubber tires to tractors. The innovation quickly spread industry-wide, as (to many farmers' surprise) it improved tractive force and fuel economy in the range of 10% to 20%. Within only 5 years, pneumatic rubber tires had displaced cleated steel wheels across roughly half of all tractors sold industry-wide. Cleated steel remained optional equipment into the 1940s. Also in 1932, Allis-Chalmers acquired the Ryan Manufacturing Company, which added various grader models to its construction equipment line. In 1933, Allis-Chalmers introduced its Model WC, its first-generation row-crop tractor, which would become its highest-selling tractor ever. In 1937, its lighter and more affordable second-generation row-crop, the Model B, arrived, and also became a top seller. Its All-Crop Harvester was the market leader in pull-type (tractor-drawn) combine harvesters. In October 1937, Allis-Chalmers was one of fourteen major electrical manufacturing companies that went to court to change the way labor unions excluded contractors and products in the building trades through the union use of the "Men and Means Clause". The action of Allis-Chalmers and others eventually resulted in the U.S. Supreme Court decision of June 18, 1945, that ended certain union practices that violated the Sherman Antitrust Act. 1940s World War II caused Allis-Chalmers, like most other manufacturing companies, to become extremely busy. As happened with many firms, its civilian product lines experienced a period of being "on