The fissionable material is the big part. But don't underestimate technical details like the shaped & coordinated charges, etc. A few years ago the US governmen

The fissionable material is the big part. But don't underestimate technical details like the shaped & coordinated charges, etc. A few years ago the US government posted all of the documents turned over from Iraq's nuclear program. A few of those documents were taken down quick after nuclear experts warned them that they were releasing vital and hard-to-discover engineering details.