So I understand that when a nucleus is formed from its individual nucleons, that there will be a decrease in mass known as the mass defect. The mass defect can be equally converted to energy following E = mc^2 and this is the nuclear binding energy. Now, is this energy released into the environment or actually incorporated into the nucleus to hold its contents together? If it's the latter, would this be the strong nuclear force? Now in terms of fission and fusion, what is the relationship between the nuclear binding energy and these two processes? I'm confused because if the nuclear binding energy is in fact what holds the nucleus together, then how could energy ever be released from ever combining or breaking nuclei? Reading around the web, Fe has about the largest binding energy per nucleon. So two smaller atoms with less binding energy per nucleon to fuse together to create one larger atom with more binding energy per nucleon. I'm guessing the energy difference between the nuclear binding energy of the large nucleus and the two smaller is the energy that is released. However, isn't this energy needed to hold the larger nucleus together; that is, wouldn't there still be no energy released into the environment because the nuclear binding energy is inherent to the system? Thanks.