As autoworkers enter a fifth day of strikes at plants in Missouri, Michigan and Ohio, United Auto Workers President Shawn Fain has set a new deadline in the contract talks.

"If we don't make serious progress by noon on Friday, September 22nd, more locals will be called on to stand up and join the strike," he announced in a video posted to Facebook Monday night, while not revealing which plants or how many would be called on next.

Fain's strategy of limited, targeted strikes at all three American auto companies has gained widespread support among its rank and file.

On Facebook, one commenter compared it to a game of Battleship.

"He knows where all the boats are and knows exactly how to sink them!" one commenter wrote.

Simultaneous strikes against the Detroit Big 3 are unprecedented in UAW history. The roughly 13,000 auto workers already on strike account for just a fraction of the unionized auto workforce, but the threat of growing the strike has added pressure and kept the companies guessing.

"We have a long way to go, and if the company doesn't respect the demands of our workers, then we will escalate action," Fain told NPR earlier on Monday.

There has been grumbling from some factions of workers asking what's the point of striking if all 146,000 of them don't strike at once.

"So much for solidarity," one person commented.

Others expressed impatience with the latest move, commenting "Why wait til Friday? We voted to strike, let's do it."

In recent days, Fain has made clear that all options remain on the table, including an all-out strike.

Newfound militancy at the UAW

Labor historians see the deployment of this new strategy as a reflection of newfound militancy at the UAW under Fain's leadership, but also some sharp and strategic thinking about how to put pressure on companies while maintaining flexibility and limiting fallout.

"It's not the goal of the UAW to bring down Ford, GM and Chrysler," says Erik Loomis, professor of history at the University of Rhode Island and author of A History of America in Ten Strikes. "That's not the point. The point is to get a fair deal out of them."

While it's too early to say whether the strategy will work, Loomis says momentum appears to be on the side of the union, with companies having to guess which part of their supply chain might be hit next.

"It does create a scenario in which the companies can't really prepare," he says.

Conserving the $825 million union strike fund

Already, there have been ripple effects impacting non-striking workers. On Friday, Ford put 600 workers on temporary layoff, because they need to use materials that need to be coated by the paint department, which is on strike.

GM has warned it will lay off 2,000 workers at a plant in Kansas early this week because it lacks components supplied by GM's Wentzville, Mo., plant, which is on strike.

The UAW said it will provide those workers who are laid off in response to the strikes the same pay as striking workers — $500 a week. For most auto workers on the production line, that represents well under half their weekly earnings.

So as not to burn through its $825 million strike fund too quickly, Loomis says it's entirely possible the union will eventually send some striking workers back to their jobs while bringing others out.

"Nobody really wants to be on the picket line for months on end," he says. "Really long strikes do not generally win."

Still for now, those on strike will remain on strike, Fain said in his video statement.

"We're going to keep hitting the company where we need to, when we need to," he said.

No breakthrough yet, but no breakdown either

While there doesn't appear to be a big breakthrough in the negotiations so far, Fain has emphasized that the talks have not broken down, as President Biden suggested last week.

"A strike is not an indication of an impasse," explains Sharon Block, executive director of the Center for Labor and a Just Economy at Harvard Law School.

"It's an indication of the parties just using a different tool — another tool — to try to change the dynamics at the bargaining table."

Sources familiar with the talks say the parties continue to bargain in good faith, meaning there has been movement on both sides.