Why Lars Klingbeil Says the Iran War Is Driving Bond Yields Higher

Lars Klingbeil’s explanation is that the recent global rise in government-bond yields is a spillover from the Iran conflict, not simply a German budget story. Germany’s finance minister and vice chancellor said the war had created global uncertainty, pushed up energy costs and revived inflation fears—pressures that can raise borrowing costs across markets. 14

That argument connects three developments: tighter oil flows through the Strait of Hormuz, a more persistent inflation risk and a sell-off in longer-dated government bonds. It also helps explain why Germany’s fiscal outlook has deteriorated, while leaving an important caveat: war-related risk amplified existing concerns about deficits, debt supply, growth and monetary policy rather than replacing them entirely. 1

How the energy shock reached bond markets

The Strait of Hormuz is a crucial route for Middle Eastern energy shipments. As traffic through the waterway slowed and its reopening became uncertain, oil markets priced in a greater risk of prolonged supply disruption. Reuters reported that crude flows through Hormuz had fallen sharply from their pre-war average, while Brent prices stabilized around $90 a barrel as traders considered the possibility that restrictions could last for months.

Higher oil and fuel prices can feed into headline inflation and inflation expectations. For bond investors, that creates a risk that central banks will need to keep interest rates higher for longer, or will have less room to cut them. Long-dated bonds are particularly vulnerable because their prices reflect expectations about inflation and interest rates over many years.

The result is an inverse price-yield move: when investors sell existing bonds, their prices fall and their yields rise. The U.S. 30-year Treasury yield reached an intraday high of 5.321% on August 18, its highest level since June 2007, as investors weighed the inflation consequences of the worsening conflict. Germany’s 30-year government-bond yield reached 3.79%, its highest level since 2011, according to reports citing market data. 1

Why equities also came under pressure

The same shock affects stocks through two channels. Higher energy costs can squeeze corporate margins and reduce household purchasing power. At the same time, higher bond yields raise the discount rate used to value future corporate earnings, which can put pressure on equity prices.

Those concerns were visible when oil prices rallied and Wall Street fell as traders became less confident about an agreement that could stabilize the region and reopen the Strait of Hormuz. European shares and futures also faced pressure as investors reassessed the inflation outlook. 19

This is why the market reaction was broader than a bond-market repricing. Investors were simultaneously assessing weaker growth, higher input costs and the possibility that central banks would remain restrictive for longer.

The central-bank dilemma: inflation or growth?

The conflict creates a difficult policy trade-off. A supply shock that raises fuel prices argues for caution on interest-rate cuts because inflation could become more persistent. But the same shock can weaken consumption, manufacturing and investment, which argues for lower rates to support economic activity.

That combination is often described as a stagflationary risk: weaker growth alongside higher inflation. Reuters reported that central-bank chiefs were meeting against a backdrop of a prolonged Hormuz closure, rising crude prices and a sell-off in long-dated U.S. debt.

For policymakers, the key question is whether the energy shock is temporary or becomes embedded in wages, prices and expectations. The available reporting shows that markets were concerned about the latter, but it does not establish that the conflict alone would determine future interest-rate decisions.

Why Germany’s fiscal outlook worsened

Klingbeil also linked the conflict to Germany’s weaker growth and lower expected tax receipts. The logic is particularly important for Germany because its manufacturers are exposed to energy costs: more expensive fuel and electricity can reduce production, profits and employment, weakening the tax base. 37

Germany’s tax advisory council subsequently reduced its projected total tax revenue for 2026–2030 by €87.5 billion compared with its previous forecast. The council expected federal revenue in 2026 to reach about €382 billion, roughly €9.9 billion below the earlier estimate.

Other reporting put the cumulative federal shortfall through 2030 at about €52.3 billion, illustrating the difference between the federal-government figure and the broader estimate covering federal, state and local authorities. The downgrade adds pressure to a budget already facing deficits and competing spending demands.

Klingbeil presented those figures as evidence of the economic cost of the war. But a revised tax forecast is not a precise accounting of one event’s impact: it incorporates assumptions about growth, energy prices, trade and other economic conditions. The conflict is therefore best understood as a major additional shock, not necessarily the sole cause of Germany’s fiscal deterioration. 1

What the U.S. Treasury did to calm long-term yields

The U.S. Treasury responded to the long-end bond sell-off by increasing its planned buybacks of longer-dated nominal coupon securities. The operation size was raised to at least $4 billion per transaction, up from $2 billion, with the increase expected to add at least $14 billion to the quarter’s planned purchases.

Buybacks can support market liquidity by creating additional demand for bonds that investors are trying to sell. The announcement initially pushed global long-term yields lower: the U.S. 30-year yield fell by roughly nine basis points in the immediate reaction.

The relief did not fully resolve the underlying problem. Yields later moved higher again as investors continued to focus on inflation and the scale of government borrowing. That short-lived response shows the distinction between a market-functioning intervention and a policy that changes the long-term fiscal or inflation outlook.

The main takeaway

Klingbeil’s account is a clear transmission story: the Iran conflict disrupted energy flows, higher oil prices revived inflation concerns, investors sold longer-dated bonds and borrowing costs rose. Germany then faced a second-order fiscal effect as weaker growth translated into lower projected tax revenue. 13

The caveat is causality. The conflict appears to have intensified pre-existing bond-market pressures, including concerns about government debt, deficits and future interest rates. The Treasury’s buyback announcement could improve liquidity and temporarily lower yields, but it could not by itself remove those broader risks. 1