Litton Financial Printing Division (defendant) printed checks using hot- and cold-type printing processes. A union represented its employees under a collective-bargaining agreement (CBA) with a broad, unlimited arbitration clause. A seniority clause read, “In case of layoffs, lengths of continuous service will be the deciding factor if other factors such as aptitude and ability are equal.” A year after the CBA expired, Litton eliminated cold-type operations and laid off 10 employees who worked primarily or exclusively with that process, including six of its most senior employees. The union filed a grievance claiming the layoffs violated the seniority clause, but Litton refused to arbitrate. The National Labor Relations Board (NLRB) found Litton violated its duty to bargain. The appellate court affirmed under Nolde Bros. v. Local 358, Bakery Workers Union, 430 U.S. 243 (1977), which found the duty to arbitrate may survive a CBA’s expiration. The Supreme Court granted review.