Trenches and Tablets: Part III – From FM 3-90 to Mosaic

FM 3-90 taught us to fix and flank. Ukraine taught us to find, fuse, and fire—faster. What’s emerging isn’t a new playbook—it’s a battlefield mosaic, where every sensor and shooter plugs into a fluid, self-healing warfighting web.

Photo by U.S. Navy Special Warfare

How the U.S. Army’s Bedrock Doctrine Is Getting Smashed and Rewired in Real Time

FM 3-90 is a foundation. Fire and maneuver. Fix, flank, finish. Classic combined arms. It’s been the Army’s tactical gospel for decades. But guess what? The battlefield doesn’t care.

Ukraine has exposed something we all sort of knew but didn’t want to say out loud: FM 3-90 is a brilliant doctrine for a previous war. In this one, everything is a sensor, everything is a target, and the battlefield is a tangled web—not a linear front.

That’s where mosaic warfare comes in. It’s not in the FM yet—but it’s in the fight. And it’s dragging doctrine along for the ride.

What Is Mosaic Warfare?

At its core, mosaic warfare is the idea that modular, distributed combat elements—drones, sensors, shooters, jammers, decision-makers—can be recombined dynamically like tiles in a mosaic, responding to threats in real time.

Think: not a battalion fire plan with prep phases and timed maneuvers, but a kill network that self-heals, reconfigures, and keeps firing even as chunks get blown away.

Instead of:

“Alpha Company suppresses, Bravo flanks,”
…you get:
“Sensor 1 finds, Drone 2 confirms, AI node 3 sends fire mission to Battery 4 while Operator 5 confirms BDA.”

All in minutes. No brigade plan. No TOC choreography. Just responsive, node-based lethality.

Why FM 3-90 Can’t Keep Up

Let’s be clear—FM 3-90 still teaches fundamentals we’ll always need: combined arms integration, security tasks, movement to contact. But here’s where it starts breaking down:

  • Centralized decision-making = delay = death
  • Linear formations = predictability = targeting
  • Dedicated recon = single point of failure
  • Tempo managed at the company level = too slow for drone-fed fires

Ukraine showed us that the real tempo of LSCO is being driven by firepower-on-demand, not maneuver-phased assaults. Units are building ad-hoc fire webs. Not fire plans. And when one drone or team gets knocked out, another node picks up the signal. That’s mosaic.

The New Doctrine in the Making

The shift is already underway. You can see it in:

  • TRADOC Pam 525-3-1: Army Operating Concept 2028 (Multi-Domain Operations)
  • FM 3-0 (2022): Operational doctrine embracing convergence and distributed C2
  • RAND’s Mosaic Warfare studies on disaggregated sensor-shooter networks
  • DARPA’s ACE and OFFSET programs building autonomous tactical swarms
  • And NATO experimentation with MUM-T (manned-unmanned teaming) at the brigade level

What’s emerging is a doctrinal language of nodes, webs, and distributed control—a very different beast than 3-90’s phased fire and movement framework.

Ukraine: The Mosaic in Action

Ukrainian units are already doing this:

  • Loitering munition scouts locate targets
  • Dismounted teams verify from visual overwatch
  • Fires cells slaved to Starlink respond autonomously
  • Damage assessments feed straight back to drone teams

And if any node drops offline? Another one picks it up. It’s combat redundancy through distribution.

Imagine every team not as a “platoon” in the org chart, but a smart tile—autonomous, lethal, swappable.

Challenges Ahead

Switching to mosaic thinking isn’t just tech—it’s cultural.

  • Commanders must give up control. (That’s hard.)
  • Comms must be resilient, not hierarchical.
  • Fires authority must decentralize.
  • Training must shift from formation warfare to network warfare.

This doesn’t mean throwing out FM 3-90. It means layering new doctrine on top of it—the way you’d layer a digital battle management app on top of a paper map. Both have value. But one gives you the edge in a compressed, sensor-rich, AI-assisted battlespace.

Final Word

FM 3-90 got us through the last war. Mosaic warfare might get us through the next one.

Ukraine didn’t just write a new doctrine—they lived it, one blood-soaked kill chain at a time. What they’re building isn’t clean or perfect. But it’s fast, modular, and deadly. And it’s what modern warfare is becoming, whether the manuals catch up or not.

“In tomorrow’s war, your formation isn’t what you draw on the whiteboard. It’s whatever survives and can still shoot.”