This is extremely off topic, but since I know you are former intelligence, the difference between the DIA and the CIA has never been clear to me. They seem to have similar interests and skill sets.
The audiences are ostensibly different. The DIA produces intelligence for military use, so that's going to almost totally very closely monitoring the military forces of other nations, not paying much attention to their other national activities. CIA is monitoring everything else and also maintaining an overview of military activities. There are other
foreign intelligence activities going on as well. The State Department has its foreign intelligence activity, for instance.
Sometimes they overlap, such as with the question of "Is Iraq going to invade somebody?" The DIA was looking purely at how they were arraying their forces, calling up reserves, et cetera. Saddam Hussain was using the Soviet playbook, and everything he was doing was step-by-step right out of their chapter on "How to Invade Your Neighbor." The CIA, OTOH, didn't think it made good political sense for Saddam to invade Kuwait or Saudi Arabia and risk the ire of the US.
Official disagreements between the DIA and CIA happened many times during my career. Another time regarded "stockpiles of WMD" in Iraq. DIA said, "They don't have them" (and a number of people in the Pentagon lost their jobs over that). CIA--under considerable arm-twisting from Vice-President Cheney--said, "Well, they want them and they'd have them if they could...okay, maybe they have some...but the possibility of the converse cannot be denied." However, only CIA can speak directly to the president, so DIA just has to convince CIA or just sit on their opinion.
It also happened a couple of times that I know of when DIA discovered something CIA knew and wasn't telling anyone...and wanted us to keep mum as well. By "keep mum" I mean not even tell our own chain of command...which we considered balderdash every time. It was hard enough getting our operators to trust "intel" without actually keeping secrets from them. That kind of nonsense happened at the senior levels.
Usually, though, down at the desk analyst level, we all knew our colleagues at the other agencies and shared thoughts and information. Sometimes we even published joint analytical reports and had kind of an etiquette in how we gave each other billing on the report, like "....with Significant Contribution by John Doe, CIA."