What's the Name of That Book??? discussion

I read a book a couple years ago about these kids who are sent back in time. When they get to the past they wake up in a dark room and there is people sleeping in a room near them. Later on they end up having to fight in a war. After that when some of their kids who were sent back are eating. A couple are pulled from the past and meet someone and are watching the other kids who were not pulled eating in the past still. They return to the present later on and find out that the kids that were left there were from that time period and that they were kidnapped from the past some years ago. And that there is a lot more children in the present who are from the past. I believe it ends with one of the kids who was sent to the past walking his dog and meets the guy who sent them to the past again. I would appreciate any help you could give me for finding out the title of this book. I also believe the cover of the book was purple and might have had like a castle tower or wall or something like that on it.

I am kind of unclear on what you are saying, but the parts I did get sound like The Missing series by Margaret Peterson Haddix.
The first book is Found, but you seem to be talking about the sequel Sent.
This is the cover:

It's a really great series!

That's it! Thank You!