HARRISBURG, Pa. — Nippon Steel and U.S. Steel said Wednesday they have finalized their “historic partnership,” a year-and-a-half after the Japanese company first proposed its deal to buy the iconic American steelmaker for nearly $15 billion.

The agreement calls for Nippon Steel to invest roughly $11 billion across U.S. Steel’s domestic operations over the next three years, a move the companies say will protect and create more than 100,000 jobs.