The war may be fading. The bond market is not. Since the announcement of the fragile US-Iran agreement, investors have rushed to celebrate the return of lower oil prices. Brent crude has retreated sharply. Inflation fears have eased. Equity markets have recovered. The consensus is rapidly rebuilding around a familiar narrative: the worst is over. The bond market disagrees. Despite falling energy prices, government borrowing costs remain stubbornly high across the developed world. US Treasuries, German Bunds and UK Gilts have all failed to stage the rally many investors expected. More importantly, real yields, the true cost of capital after inflation, continue moving higher.

That changes everything. Because markets are no longer pricing an inflation problem. They are pricing a credibility problem. For months, investors assumed higher bond yields reflected temporary inflation fears triggered by the Iran war. That explanation is becoming increasingly insufficient. The latest market moves tell a different story. Real yields have accounted for most of the rise in government borrowing costs since the conflict began. In other words, investors are demanding higher returns not because they fear inflation alone, but because they believe the world has fundamentally changed. The era of structurally low interest rates is ending. And governments are only beginning to realise it.

The reasons are accumulating. Public debt continues to explode. Defence spending is rising almost everywhere. Energy security requires hundreds of billions of additional investment. Artificial intelligence is generating an unprecedented investment cycle in infrastructure, semiconductors and electricity. Ageing populations continue to place enormous pressure on public finances. Meanwhile, central banks are no longer absorbing unlimited quantities of government debt. The buyer of last resort has quietly stepped away. This explains why markets remain remarkably sceptical despite the easing of geopolitical tensions. The reopening of the Strait of Hormuz undoubtedly reduces one source of inflationary pressure. Lower oil prices should gradually feed through into transportation, manufacturing and consumer prices. But lower oil prices do not reduce fiscal deficits. They do not reduce debt issuance. And they certainly do not eliminate the growing supply of government bonds flooding global markets. That is the real story.

The bond market is no longer asking whether inflation will fall. It is asking who will finance the government. The United States illustrates the dilemma perfectly. Despite expectations that the Federal Reserve will leave rates unchanged this week, investors are already pricing the possibility of renewed tightening in 2027. This may appear contradictory. It is not. Markets increasingly believe that the neutral rate, the level of interest rates that neither stimulates nor slows the economy, has permanently moved higher. This is perhaps the most important macroeconomic shift of the decade. For nearly fifteen years, governments operated under the assumption that money would remain almost free indefinitely. Every crisis justified more borrowing. Every recession justified more stimulus. Every geopolitical shock justified more spending. Now investors are demanding compensation. And they are becoming increasingly selective.

Europe faces a similar challenge. Although the ECB has already started tightening and may continue raising rates over the coming months, Europe remains structurally vulnerable to imported inflation. Even if energy prices normalise, rebuilding strategic reserves, diversifying supply chains and strengthening defence capabilities will require massive public investment. Those bills have not disappeared. They have only been postponed. Japan tells exactly the same story. For decades, Japanese investors helped finance the world through extraordinarily low domestic interest rates. Today, the Bank of Japan has finally begun normalising policy. As Japanese yields rise, domestic investors have less incentive to buy foreign government bonds. One of the world’s largest providers of global liquidity is slowly retreating. The timing could hardly be worse.

For financial markets, the implications extend well beyond sovereign debt. Higher real yields tighten financial conditions across the entire economy. Mortgage costs remain elevated. Corporate borrowing becomes more expensive. Equity valuations face increasing pressure. Banks holding large portfolios of long-duration government bonds continue suffering mark-to-market losses, keeping liquidity risks alive beneath the surface. The bond market is quietly repricing the entire financial system. And there is another implication that investors continue to underestimate. The dollar. Historically, higher US yields have supported the dollar by attracting foreign capital. But this relationship becomes more fragile when yields rise because investors question fiscal sustainability rather than economic strength. There is a profound difference between yields rising because growth is strong and yields rising because governments must pay investors more to finance expanding deficits. The first supports the currency. The second eventually weakens confidence in it. This distinction may become increasingly important over the coming years.

The irony is remarkable. Markets spent months obsessing over oil. The bond market has already moved on. Its message is becoming increasingly difficult to ignore. The geopolitical crisis may have eased. The fiscal crisis has only just begun. And unlike wars, governments cannot negotiate with mathematics.