On the campaign trail, Trump promised to rebuild the U.S. military that former President Obama had sought to gut.

In fact, Trump’s budget plan does add funds to Pentagon spending, while cutting some social programs, but it may not be enough.

Secretary of Defense James Mattis apparently has some misgivings about Trump’s budget. Namely, the $603 billion proposed just won’t do the trick.

Mattis has not spoken out against the spending plan publicly. But privately, the defense chief has told lawmakers that even with the proposed boost in funding, the Pentagon would not receive enough to do everything Trump has proposed.

“Mattis continues to express to members of the Armed Services Committees that he’s being thwarted getting his message out that $603 billion is insufficient to do what Trump has called for,” one Republican lawmaker told CNN.

Rebuilding the military is going to take more than just convincing more able-bodied individuals to sign up – and that does need to happen.

The Air Force needs more fighter jets and the U.S. Navy needs more boats.

Trump has taken credit for Lockheed Martin’s adjustment to the $100 million-per-unit cost of the F-35 fighter jet program.

Maybe he can start talking about bringing down the cost of carriers and battleships, next.