More than 6,500 Samsung Electronics workers walked off the job Monday to stage a rally demanding better pay, beginning the biggest organized labor action in the South Korean conglomerate’s half-century history.

Disgruntled employees and union supporters gathered in the pouring rain outside one of Samsung’s biggest chipmaking complexes south of Seoul. Wearing red headbands proclaiming "total strike” and black raincoats, they chanted slogans and sang songs with raised fists. Union leaders, who provided the initial tally of participants, hope the highly publicized protest galvanizes a three-day walkout that will send a message to Korea’s biggest company.

Samsung’s largest union has spent weeks preparing for the walkout, after negotiations over pay and vacation time collapsed last month. This envisioned action marks an escalation from a single-day strike in early June — the first in Samsung’s 55 years of existence. It’s intended to send a message by disrupting production at one of the company’s most advanced chip facilities, union leaders say.