With GM’s union workers going on strike this week, a lot has changed operationally since the last nationwide strike against GM in 1970.

Lean supply chains were a yet-to-be-discovered concept then. Most manufacturers had lots of inventory buffers that could be used if a strike disrupted an isolated point in the supply chain, or to continue to assemble products with temporary workers from management or outside sources.

Now, however, with the practice and its just-in-time inventory philosophy widely deployed in automotive and many other supply chains, those inventory buffers are long gone. That means a strike or other disruption at an internal component supplier can lead to critical parts shortages in a matter of days – or maybe even hours.

While outsourcing an increasing level of the parts used for assembly, US automakers still have substantial component production operations that feed the assembly plants. That makes their options during a strike very limited.

Wildcat strikes in just two GM parts plants in 1998, for example, soon basically closed nearly all of the company’s assembly operations within days.