Former Trump National Security Adviser Robert O'Brien reacted to the Heritage Foundation 2023 Index of US Military Strength ranking military branches like the Air Force as "very weak" and the Navy as "weak." On "Fox & Friends" Wednesday, O'Brien said he's "very concerned" because the report calls into question whether the military can effectively fight one war at the present time.

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ROBERT O'BRIEN: What's so worrying about this report is that the US military used to be designed to be able to fight two and a half wars. This report says we may not be able to fight one war effectively. It's very concerning. We need to rebuild the military. We need to replenish the stocks of everything that we've sent to Ukraine. We're low on missiles, we're low on javelins. We're low on stingers. We can't supply them to Taiwan now. We need to modernize our nuclear triad at a time that Vladimir Putin and the Chinese are threatening us with nuclear war. 

U.S. Defense Secretary Lloyd Austin

U.S. Defense Secretary Lloyd Austin attends a news conference following a NATO Defence Ministers meeting in Brussels, Belgium, Feb. 17, 2022. REUTERS/Johanna Geron (REUTERS/Johanna Geron)

We need to rebuild the Navy, which is in terrible shape right now. We had a plan to build a 355-ship Navy. That's sidelined now. And the Navy is trying to retire some of our best ships, our cruisers, our guided missile cruisers. And we've got to get this recruitment crisis under control and start inspiring young Americans to join the service again. And so there's a lot to do. And unfortunately, we're not spending the money. There's a nominal increase in defense spending, but it's been wiped out and eaten up by inflation. So the small increase is actually a massive decrease because of the inflation that we're facing.