US leaders who want to send billions more in aid to Ukraine need to ask what kind of war they're willing to pay for

• The final weeks of the current Congress will feature debate over another aid package for Ukraine.
• Before opening the checkbook again, lawmakers need to ask how they want this war to end and how more aid will bring it about.

While national attention may be focused on the winners and losers of the midterm elections, a high-stakes contest in the lame-duck session of Congress is just beginning.

House Republican Leader Kevin McCarthy ignited a firestorm of criticism when he commented that Ukraine may not be able to expect a "blank check" of American aid in the new Congress. Both House Speaker Nancy Pelosi and Senate Republican leader Mitch McConnell have since vowed to rush more assistance to Ukraine before the end of the year.

Before Washington opens the checkbook again, lawmakers need to subject aid proposals to a simple Petraeus Test. Gen. David Pretraus, who oversaw the American surge in Iraq, often exposed the assumptions of plans presented to him with a simple command: tell me how this ends.

So far, the story of American support of Ukraine against Russia's terrible invasion attempt has been one of unhesitating generosity. The Biden administration has committed more than $19 billion in security assistance and Congress has approved nearly $66 billion in total funds for Kyiv since the start of the war in February.

But how does this end? Unlike Stinger missiles and Humvees, that tough but crucial line of questioning has been in short supply.

Currently, Russia and Ukraine are locked in a stalemate. Russian offensives have continually underperformed and been frustrated. With winter looming and the hope for a quick victory all but evaporated, each side is increasingly dug in.

For Ukraine, ceding even an inch is an unacceptable reward for Russia's barbaric invasion. Meanwhile in Moscow, President Vladimir Putin's political (and perhaps even personal) fate now depends on the ability to claim victory as a growing number of Russian soldiers return in body bags.

If the two sides are headed toward an indefinite period of fighting to the last man, Washington must be clear-eyed about the fact that there are no core American national security interests at stake. Ukraine is now increasingly requesting American economic support to keep the Ukrainian energy sector, schools, and government running as the war drags on.

America must not sleep-walk into becoming ever more invested in a distant conflict that is tragic but secondary in strategic importance. The recent painful withdrawal from Afghanistan should serve as a reminder of how even the most justified mission can quickly morph into years- and even decades-long quagmires with no satisfying total victory.

The need to be realistic is all the more important when considering that America is now increasingly underwriting a war of attrition against a nuclear power desperate to save face. Some members of Congress have explicitly called for America to make an open-ended and long-term commitment to Ukraine in the lame-duck session.

Two things can be true at the same time: Russia's war of aggression is utterly abhorrent and it makes no strategic sense for America to endlessly promise more support for Ukraine. Such a commitment would be reckless, encouraging Ukraine to ignore opportunities for a negotiated peace with Russia and incentivizing Russia to escalate the conflict to the point of challenging America to either directly enter the conflict or back off.

Neither outcome is preferred, but thankfully both can be avoided with increased foresight in the current aid conversation. Any future American assistance to Ukraine must be conditioned on Kyiv's willingness to continue settlement talks with Russia. Likewise, Washington's diplomatic and economic pressure on Moscow should aim to incentivize a negotiated end to the war.

Members of Congress owe it to American taxpayers to thoughtfully pause before shoveling more resources into a war on the other side of the planet. At the very least, legislators must push advocates of more aid for Ukraine to explain exactly how America's national security would be enhanced. The Pentagon's ongoing struggles to track the end users of weapons already transferred to Ukraine should only add to this rightful skepticism.

As the debate in Washington intensifies and the pleas from the battlefield continue to stream in, cooler heads must prevail in remaining laser-focused on the likely costs, benefits, and liabilities of any future aid to Ukraine.

Just one simple request should echo through the hallways of Capitol Hill during this lame-duck session: Just tell me how this ends.

Andrew C. Jarocki is a master's student at the McCourt School of Public Policy at Georgetown University. He formerly served as the editor-in-chief of Realist Review, and his work has appeared in Defense News, The National Interest, and Responsible Statecraft.