What happened to the US long-end on Monday?

That was the question — or one question, anyway — floating around Wall Street following a rollercoaster ride for equities, which managed to close mostly unchanged following a farcically turbulent session during which traders and investors pondered the prospect of world-ending tariffs.

Bonds, which had been relentlessly bid into the stock selloff, took an abrupt turn to start the week, where that means yields rose ~20bps in what counted as the worst session of 2025. At the risk of overstating the case, the range was breathtaking, particularly given the dearth of data on offer.

The ~35bps range for the 10-year was among the widest since March of 2020, when Treasurys were at the epicenter of several overlapping dramas as the pandemic took hold. The long bond likewise traded in a 30bps range on Monday.

The outsized selloff erased a quarter of the progress Scott Bessent made this year on his stated goal of bringing down 10-year yields, a crutch he’s leaned on while ludicrously intimating that an increasingly egregious stock selloff and rising recession odds are all part of the Trump administration’s masterplan.

So, what happened? Well, the conspiratorial among you might be inclined to suggest “someone” sold a bunch of Treasurys to send a message to Donald Trump. (“The long-end sleeps with the fishes.”) Still another argument says the Trump administration’s antics are by now undermining the world’s faith in America’s debt. A less nefarious explanation is just that a lot of folks need to raise cash amid the global bloodletting, and Treasurys were offloaded to raise dollars.

There are a variety of other explanations, and BMO’s Ian Lyngen did a characteristically good job of laying them out on Monday evening. Here’s a truncated excerpt from his afternoon note, presented without further comment:

First, Trump appears to have miscalculated the response of the US’s major trading partners. A reality that suggests we’re due for even higher imported inflation than previously projected. Second, if the Administration’s goal was to replace income tax revenues with tariffs, the budget just got harder to balance in the event the trade war leads to greater demand destruction, raising the question, How does Trump’s agenda get funded now? More Treasury issuance is the clear risk. There has also been increased chatter regarding the potential for investors to step away from this week’s Treasury auctions as a precaution against the potential for a foreign buyers’ strike. To be clear, we are not expecting foreign buying to drop substantially at the auctions, rather this has simply been a risk highlighted by several astute clients. The third contributor to the selloff is the idea that Treasury supply will become increasingly difficult to underwrite in the event that the trade war is a material challenge to the US Dollar’s status as the reserve currency.