Which big could the trench rats grow?

There's no evidence that "trench rats" grew to any unusual size during World War I. While rats were a serious problem in the trenches, they were still just regular rats.

Here's what we know:

* Rats are opportunistic: They thrive in areas with plenty of food and shelter, which the trenches provided.

* Rats reproduce quickly: This meant their numbers could increase rapidly in the cramped conditions of the trenches.

* Rats carry diseases: This made them a health hazard for soldiers.

However, there's no historical record of rats becoming abnormally large in the trenches. The stories about "giant rats" are likely exaggerated or based on soldiers' fears and anxieties.

It's important to rely on accurate historical accounts and not on folklore or sensationalized stories.