(Reuters) -More than 1,000 Starbucks ( SBUX ) unionized baristas launched an open-ended strike on Thursday, intensifying their push for a collective bargaining agreement over pay and other benefits at the coffee giant.

Starbucks Workers United has repeatedly targeted the company's Red Cup Day - one of its busiest days - when customers receive free reusable holiday-themed cups with coffee purchases.

Here is a timeline of the key moments in Starbucks' ( SBUX ) negotiations with its union:

December 2021:

Starbucks ( SBUX ) workers in Buffalo, New York, voted to unionize, forming the chain's first U.S. unionized store with Workers United.

May 2022:

Over 50 Starbucks ( SBUX ) cafes voted to unionize and former U.S. President Joe Biden met with organizers from Starbucks ( SBUX ) and Amazon.

November 2022:

Workers at more than 100 U.S. company-owned Starbucks ( SBUX ) locations staged a one-day "Red Cup Rebellion" over alleged retaliation against union activity.

June 2023:

About 3,000 workers from over 150 stores walked out over claims of banned Pride decorations, prompting new company guidelines.

November 2023:

Employees at hundreds of Starbucks ( SBUX ) stores walked off their jobs during the company's Red Cup Day event, and the company later said it would raise the hourly pay of U.S. retail workers by at least 3% from 2024.

February 2024:

Starbucks ( SBUX ) and the Workers United union said they agreed to create a "framework" to guide organizing and collective bargaining and potentially settle scores of pending legal disputes.

December 2024:

Starbucks ( SBUX ) union members at over 300 stores walked out over pay, staffing and scheduling issues.

January 2025:

Starbucks ( SBUX ) and its union agreed to bring in a mediator to aid stalled contract negotiations and reach a deal.

April 2025:

Starbucks ( SBUX ) union delegates involved in contract bargaining voted to reject the coffee chain's latest proposal that guaranteed annual raises of at least 2%.

November 2025:

More than 1,000 Starbucks ( SBUX ) employees in over 40 U.S. cities launched an open-ended strike, which the union has said could become the longest and largest strike in the company's history.