Treasury Secretary Bessent took aggressive action this week, first issuing a public warning against shorting the yen, which drove the currency higher, then significantly expanding Treasury buyback operations to contain long-end yields. The outcome left the yen stronger but Treasuries under renewed pressure.

Each strategy holds its own logic, yet together they pose a twin threat to the four-year bull market in US stocks—yen strength undermines carry trades, while rising yields compress equity valuations.

On Wednesday, US equities fell for a third consecutive session. The Dow dropped over 400 points, down 0.8%; the S&P 500 slipped 0.5%; and the Nasdaq declined 0.6%, with AI tech stocks bearing the brunt of the selling.

A 'Pea Shooter' Response in Treasury Buybacks Falls Flat

The Treasury announced Wednesday it would raise the cap on single long-dated bond buybacks to $6 billion, triple the scale initially planned for the prior month. But the market response was one of disappointment.

Bessent had previously hinted that buybacks could exceed $4 billion, fueling Wall Street expectations the single-operation ceiling might reach $8 billion to $10 billion. When the $6 billion figure landed, yields moved up rather than down. The 10-year Treasury yield touched 4.836% intraday, its highest since October 2023, while the 30-year yield reached 5.285%, edging toward the 5.30% peak seen last month.

Elias Haddad of Brown Brothers Harriman & Co. put it bluntly: "Right now, the Treasury has shown up to a tank battle with a pea shooter."

Deutsche Bank strategist Steven Zeng noted, "It's like the Treasury created a monster that now has to be continuously fed," pointing out that the $6 billion announcement failed to deliver the "shock and awe" investors anticipated.

Later Wednesday, the Treasury auctioned $39 billion in 10-year notes at a yield of 4.834%, setting a record high for that maturity's auction history.

Dustin Reid, chief fixed income strategist at Mackenzie Investments, said, "It's still early days in how they manage this situation. The Treasury certainly won't be pleased with the market's reaction today."

Bessent Concedes He Cannot Control the 'Equilibrium' Price

In the face of intense market pushback, Bessent acknowledged at a Texas event Tuesday that he cannot alter the "equilibrium" price of Treasuries, with his goal limited to slowing the pace of price swings and preventing harmful narratives from taking hold. He attributed the rapid rise in long-end rates to market fears of "US insolvency," calling such worries "absurd, but briefly a dominant narrative."

Wells Fargo macro strategists Angelo Manolatos and Francis Brown wrote that "additional catalysts are needed to push long-end yields lower," including slower growth and inflation, lower energy prices, reduced Fed policy uncertainty, fiscal consolidation, or a contraction in corporate bond issuance. None of these conditions currently apply. High oil prices continue to lift inflation expectations, and markets now price a 62% probability of a Fed rate hike at next week's FOMC meeting. Corporate bond issuance is also at a seasonal peak this week, with 18 borrowers tapping the market Tuesday, marking the year's third busiest day.

'I'm the House'—Propping Up the Yen, but at What Cost?

The day before the Treasury buyback setback, Bessent issued a stark warning to yen short sellers at the same Texas event, stating, "I'm the house now, so when we intervene on the yen, I know exactly what the Japanese, the Bank of Japan, and Japanese policymakers are going to do. If you want to bet against me, feel free."

His confidence draws from two sources: direct knowledge of Japanese policy moves and expectations that the Bank of Japan will raise its benchmark rate by 25 basis points this month. The yen extended gains Wednesday, touching 153.49 per dollar intraday, after posting its strongest level since February the prior day.

The problem, however, is that yen strength is not good news for US stocks.

Yen Gains Set the Carry Trade 'Ticking Bomb'

The yen has long served as the world's cheapest funding currency. A typical carry trade involves borrowing low-yielding yen, converting to dollars, and buying high-return assets like US tech stocks. A stronger yen raises the cost of these trades, forcing holders to unwind positions.

Steve Sosnick, chief strategist at Interactive Brokers, said the yen's current momentum "has already been enough to shake some people who borrowed yen to leverage bets on high-flying US stocks."

Rich Privorotsky, head of Goldman Sachs' Delta-One desk, noted that regardless of how one interprets Bessent's rhetoric, "the yen is objectively appreciating, and the market is betting on BOJ tightening and capital repatriation." He raised a key question: "What happens when yen carry trades unwind and funds flow back into Japanese bonds and equities?" His assessment: "The S&P and large caps feel mysteriously heavy without an obvious fundamental reason. It's worth noting that some leverage and carry positions may be quietly working their way out of the system."

Jordan Rizzuto, CIO at GammaRoad Capital Partners, framed it directly: "This is the biggest risk to the bull market."

Bessent's Bind: The Yen Can't Be Too Weak, or Too Strong

An inherent contradiction now troubles Bessent's policy framework. Foreign securities held by Japan fell by nearly $88 billion at the end of August, per MarketWatch, with Japan long established as a major holder of US Treasuries.

Rizzuto noted that if Japan has recently been selling Treasury assets, it warrants close attention—especially given it follows coordinated intervention to support the yen. "It really makes you feel the weight of these two things," he said.

The Treasury wants the yen strong enough that Japan avoids selling US bonds to raise funds. But if the yen rallies too sharply and triggers mass carry trade unwinds, the blow to US tech stocks would be far more direct. Some traders are already privately questioning whether Bessent has the causal relationship backwards—he aims to relieve pressure on long-end yields by pushing the yen higher, yet historically it is interest rate differentials that drive currency flows, not the other way around.