It's a poem, right? The 1 means that they were back to the mountain like you back to somebody (I went back to my girlfriend) The 2 means that They really went again at the mountain. The 3 they were back into the mountain. They and the mountain was interconnected again. and 4, It's happened when they climb the mountain.

1. they were back to the mountain. (incorrect?- maybe used for a specialization) 2. they were back on the mountain. - they returned to the mountain and were walking or climbing it 3. they were back into the mountain. (incorrect? - maybe used for a something they are passionate about) 4. When they back onto the mountain. - same as #2, more like climbing the mountain as they will be using ropes attached to it. another: They were back at the mountain. - they returned to the mountain area # 2 is the best and #4 is good if they are climbing the mountain Hope this helps! :) Lori

Thank Teacher Patrick Yingst very much for so detailed explanation.

Hello! The first one sounds a bit awkward, but you could say it. The subject of the sentence "they" are going back to the mountain. Normally you'd see something like "they were back to the mountain again to hunt some more deer." There would be more to the sentence because "they were back to the mountain" just doesn't sound quite right without more detail. The third and fourth sentences don't really make sense. Sentence three I guess they could be going back into caves in the mountain. Sentence four could be corrected to something like "When they were back onto the mountain" with the only change being adding "were" to the sentence. The general meaning I think these sentences is going for is "when they returned to the mountain" I hope this helps.

I think they are to want to express the same meaning, perhaps some are incorrect , which is better or best?