12 the whole assembly of Israel gathered at Shiloh to go to war against them.

Read Joshua 22:12 Using Other Translations

And when the children of Israel heard of it, the whole congregation of the children of Israel gathered themselves together at Shiloh, to go up to war against them.
And when the people of Israel heard of it, the whole assembly of the people of Israel gathered at Shiloh to make war against them.
So the whole community of Israel gathered at Shiloh and prepared to go to war against them.