Recognition strike
A recognition strike is an industrial strike implemented in order to force a particular employer or industry to recognize a trade union as the legitimate collective bargaining agent for a company's workers. They were more common in North America prior to the advent of modern labor law which usually has a process which legally compels an employer to recognize a union that has been properly certified and thus shown that it has the support of the workers in a specific bargaining unit.
See U.S. Steel Recognition Strike of 1901