The mechanism: Congress has required a 355-ship Navy since 2016. The Navy has never been within 60 ships of it, and both GAO (GAO-26-109068) and CBO now say the math doesn't close at current or even projected budget levels — not because Washington lacks the will, but because the industrial base can't physically build fast enough and the bill for fixing that keeps growing. When a force-structure goal can't be funded, it doesn't get restated — it gets quietly redefined. A "right-sized fleet" of 290-something ships costs less to promise, and a defense budget that formally trims the goal or re-phases Columbia-class boat deliveries doesn't touch backlog dollar figures already on the books. It touches the next contract — the one that hasn't been signed yet.
That's the trap in reading HII and GD off headline backlog. Backlog is signed work; growth is the next award. If a future NDAA or shipbuilding plan slows the cadence — fewer Virginia-class boats per year, a Columbia-class boat pushed a year right, DDG(X) deferred — the multi-year contracts already booked stay intact, but the annual re-up that Wall Street prices into out-year revenue shrinks or slips. Backlog looks safe. The growth rate embedded in it does not.