CNN national security analyst John Kirby, a retired rear admiral in the US Navy, was a spokesman for both the State and Defense departments in the Obama administration. The opinions expressed in this commentary are his own. View more opinion articles on CNN.

They do not fight, sail or fly under the banner of other countries, and they do not take foreign money for their work -- not in pay or benefits or any other compensation. Their obligation is to the American citizens they protect and defend, and it is not for sale.

President Trump cheapens and insults the men and women of the US military when he reduces their service to a bill of lading. He said last week that Saudi Arabia would be footing the bill to support the additional American troops he plans to send there.

"Are you ready?" he asked reporters outside the White House. "Saudi Arabia at my request has agreed to pay us for everything we are doing. That is a first. Saudi Arabia, and other countries soon now, but Saudi Arabia has agreed to pay us for everything we are doing to help them, and we appreciate that."

Trump was responding to a question about the recently announced deployment to Saudi Arabia of a small number of military personnel, aircraft and air defense capabilities. That deployment comes in the wake of Iranian attacks against two Saudi oil facilities and lands squarely amid Trump's acquiescence to Turkey's invasion of northern Syria, a move being roundly criticized on both sides of the aisle as a betrayal of the Kurdish forces with whom we have partnered to fight ISIS.

Both decisions -- to surge troops in one case and pull them back in another -- make a mockery of Trump's insistence that he wants to "bring our troops home" and "end these endless wars."

No end date has been placed on the Saudi deployment, and the Pentagon is keeping open the possibility that even more forces could be sent to the kingdom in the future. "We are taking this one step at a time," Secretary of Defense Mark Esper said last Friday. "We thought it was important to continue to deploy forces, to deter and defend, and to send the message to the Iranians: Do not strike another sovereign state, do not threaten American interests [or] American forces, or we will respond."

And by any measure, Trump's decision to turn his back on the Kurds -- after all, they "didn't help us with Normandy," he said -- will broaden the civil war in Syria and provide ISIS fresh opportunities to regain a foothold and renew attacks on US and Western targets. We may even find ourselves having to go right back in. Only next time, we won't have Kurdish partners. They've already run to Russia and Syrian President Bashar al-Assad for help.

But Trump's sheepishness in Syria and his swagger over Saudi reimbursement also raise questions about the degree to which he understands and appreciates the fundamental nature of military service and the mutual benefits American citizens accrue from having troops forward deployed.

He demeans the purposes to which these military men and women have been deployed and risks widening the yawning gap between the American people and its military.

There is certainly room for debate in this country about the nature and duration of the wars we have been fighting. It's fair, even healthy, to revisit our footprint around the world and alter our security commitments accordingly. It's even worth asking ourselves about the whole idea of national service and the continued efficacy of being defended by a professionalized force of volunteers.

But none of this debate is well served when Trump signals to our citizens that our troops are not wholly our own.

Likewise, there is the unfortunate message Trump sends to US allies and partners. Burden-sharing is a genuine concern, and Trump is right to try to persuade partner nations to increase their own defense spending and rely less on American goodwill and guns. That's been a common refrain of at least the last two administrations. And it's one that Trump has unapologetically, almost evangelically, embraced.

But when he couches it the way he does -- "Saudi Arabia has agreed to pay us for everything we are doing to help them," Trump tweeted -- he reduces foreign policy decisions to little more than bartering over a lamp at a yard sale. He denigrates the contributions of host nation forces, while at the same time letting foreign political leaders off the hook for having to make difficult decisions of their own.

Setting aside for a moment the fact that the dramatically increased tensions with Iran are of Trump's own making, the Saudis could be forgiven for thinking that this new deployment of American troops is being done not so much in our common interest, but rather in Saudi interest alone -- and therefore that US troops will be all the easier to procure in the future.

And that's really the larger shame of all this. Whether it's in Saudi Arabia or Syria or Ukraine or South Korea, Trump continues to ignore -- or at least fails to acknowledge -- the mutual benefits America enjoys from having committed friends overseas who lighten our load, provide logistics and basing support, and contribute in meaningful ways to keeping far-flung the "endless wars" he's always railing against.

To paraphrase an old boss of mine, we aren't engaged in the affairs of the world because we are a great nation; we are a great nation because we are engaged in the affairs of the world.

Those Kurdish allies he just threw under the bus ? They suffered more than 10,000 brave fighters killed in what was our once-shared mission to defeat ISIS in Syria.

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That mission isn't over. Pretty soon it may get a lot tougher. And we'll be the ones all alone.

But then, you get what you pay for.