There is a long history of members of Congress trying to get support for higher military spending by asking senior commanders if they have enough to keep America safe and strong. Since the officers are morally bound to support the president's budget -- since they didn't resign in protest when it was released -- they talk about "increased risk." So the lawmakers changed the question: What would you do with an extra billion or two? To answer that, the services devised their "unfunded priority list." Several defense secretaries in recent years tried to forbid the military from sending such lists to the Hill, but to no avail.
Now, it turns out, the Obama OMB is formally directing the Pentagon to develop such a list, with the $26 billion cap. They call it an "investment fund." It sounds to me like a way of having a DOD-wide top priority list that could be seen as more credible than individual service wish lists. Let's see how it works out.