In the early 20th century, Shenyang began expanding out of its old city walls. The Shenyang Railway Station on the South Manchurian Railway and the Shenyang North Railway Station on the Jingfeng Railway, both west of the old city, became the new commercial centers of Shenyang.[28] In the 1920s, Mukden was the capital of the warlord Zhang Zuolin, who was later assassinated when his train was blown up on 4 June 1928[29] at a Japanese-guarded railway bridge.[30] At the time, several factories were built by Zhang to manufacture ammunition in the northern and eastern suburbs. These factories laid the foundation for Shenyang's industrial development.[31]