What is the difference between retreated into and retreated back into?
They retreated into Pakistan
What is the difference between retreated into and retreated back into?
They retreated into Pakistan
I don't know what contexts you're looking for, so let's take the simplest, military. "Back" implies return to origin.
We charged the enemy lines, but met with heavy fire and loses, we were forced to retreat back into trenches.
After a day of march we encountered an enemy patrol. As they called artillery support, we were forced to retreat into a nearby town, seeking cover.
Essentially, retreat implies going away from your opposition. If you return where you started, you retreat back, but you can retreat sideways under some cover which you didn't encounter on your way there, or even further than where you came from.
The soldiers withdrew until they were back in their territory. (They could have 'retreated' and still be within enemy territory).
retreat: moving back or withdrawing. Therefore, it does not take the preposition back.
However,
they retreated (back) into Pakistan
can be parsed like this:
They retreated + (back) into Pakistan
That is, the soldiers withdrew until they were back in their territory. (They could have 'retreated' and still be within enemy territory).
not
They retreated (back) + into Pakistan
The word back may be acceptable considering that retreated here is used in its special military sense, not the general English meaning. retreat: (of an army) withdraw from enemy forces as a result of their superior power or after a defeat