With the question of whether our Army will drop to 24 brigade combat teams and 420,000 troops and the newly raised issue of how the National Guard and Army Reserve will complement the active forces, I suppose it is appropriate to link to some old publications that address the subject.
You may be interested in my old defense of a 32-brigade Army (Lord knows how long "The First Gulf War and the Army's Future" a 1997 Land Warfare Paper of the Institute of Land Warfare will last there); a synopsis of my 1999 article ("A Total Army for Total War: The Guard Divisions' Role," Army Magazine, January 1999 (Arlington, Va.: The Association of the United States Army), pp. 10-12.) on the role of the Army National Guard in providing forces to guard against a major theater war (MTW) that proves more difficult than we plan or for a MTW that expands beyond the scope of that force-planning assumption; and "The Path of the Future Army," Military Review, September-October 2000 (Fort Leavenworth, KS: US Army Command and General Staff College), pp. 91-93, which you can see here as I intended it--in stripping out charts, some continuity was lost in the text as published.
In totality, it is a view of an Army that must not shrink to a size too small to win decisively and rapidly, backed by combat units of the Army National Guard that assist as both an operational and strategic reserve.
Already, we will go to 30 active brigade combat teams and 2 battalion-sized task forces as the Army declines to 450,000 troops.
I suppose if I had my way, if the Army goes to 420,000, rather than reduce the force to 24 3-maneuver battalion brigade combat teams (plus two battalions?), I'd rather keep 32 brigade combat teams with 74 battalions.
The active force would keep 10 brigades with 3 battalions while keeping 22 brigades with 2 battalions.
The Army National Guard, with 28 combat brigades, was organized to provide 4-5 combat brigades per year that could be mobilized as an operational reserve.
I'd keep that force generation process but add an additional year in providing 12-15 battalions from those brigades after their parent brigades' year-long availability that would round-out 12-15 of our active brigades if mobilized during wartime.
So in a notional 6-year period, 4-5 brigades would spend 3 years at lower readiness, a year getting ready for their role in providing combat-ready brigades, a year as a readily mobilized brigade, and then a year where the 12-15 component maneuver battalions of the brigades remain on call to round out active force brigade combat teams.
As long as I'm wishing, with our Army lightening up and having fewer heavy brigades, I'd be happy if the National Guard would provide separate tank companies and battalions for our active infantry and Stryker brigades to give them a shot at surviving in high intensity conventional warfare against heavy enemies.