The war in Iran has reached Frankfurt. Not through diplomacy. Through inflation. The European Central Bank has raised its deposit rate by another 25 basis points to 2.5%, its second increase since the conflict began. Markets now expect more tightening, with another move possible as early as October and three additional increases fully priced by late 2027. This is not simply another ECB cycle. It is the moment when geopolitical risk becomes monetary policy. European inflation reached 3.3% in August, its highest level in almost three years. Brent is above $100 a barrel. European gas prices have returned to levels not seen since the winter following Russia’s invasion of Ukraine. The ECB now expects inflation to average 3% this year and remain above target well into 2027.

Normally, weaker growth would make a central bank cautious. Europe has complicated that calculation by refusing to weaken. Euro-area GDP expanded 0.6% in the second quarter. Manufacturing is recovering. Defence spending is rising. Infrastructure programmes are accelerating. Digital investment is supporting activity. Europe has therefore produced the combination central banks fear most. Inflation is rising. But demand has not collapsed. That gives the ECB permission to tighten. And perhaps forces it to. Christine Lagarde described the latest increase as a “no-brainer”. That language matters. It suggests the debate inside the ECB has shifted.

The question is no longer whether policy should remain restrictive. It is how restrictive it must become. A 2.5% deposit rate sits near the upper end of neutral estimates. The next increase would push monetary policy clearly into restrictive territory. That is a major change. For much of the past two years, European investors were discussing when the ECB could cut. They are now discussing how far it may need to hike. The Middle East has reversed the direction of the European rate cycle. But the more interesting consequence lies elsewhere. The ECB may now become the most hawkish major Western central bank precisely as the Federal Reserve faces a more complicated political and economic environment.

That changes currencies. If European rates continue rising while expectations for future US tightening peak eventually, the interest-rate differential that supported the dollar begins to narrow. The euro therefore gains a new source of support. Not because Europe suddenly becomes economically stronger than the United States. Because monetary policy becomes relatively tighter. EUR/USD at 1.20 or above would then no longer require a dramatic dollar collapse. Policy divergence could increasingly justify it.

This also affects European bonds. Germany has already seen long-term yields rise sharply. France and Italy face the same global repricing of duration but with much weaker fiscal starting points. An ECB deposit rate moving toward 2.75% or 3% raises financing costs just as governments borrow more for defence, energy security, and infrastructure. This creates another European contradiction. Fiscal policy is becoming more expansionary. Monetary policy is becoming more restrictive. Governments are trying to stimulate investment while the ECB raises the price of financing it. The stronger the economy remains, the easier it is for the ECB to continue tightening. But each rate increase eventually makes that resilience more difficult to maintain. That is where the risk lies. The ECB is not responding only to current energy inflation. It is worried about transmission. Higher gas prices eventually affect electricity. Higher diesel affects transport. Higher transport costs affect food. Higher energy costs influence wages. The ECB cannot let a geopolitical shock become a wage-and-services inflation cycle. So it acts before that happens.

Yet the source of inflation remains largely outside its control. Raising rates cannot open Hormuz. It cannot increase LNG supply. What it can do is make European demand weak enough to prevent those price shocks from spreading. That is a very expensive form of insurance. The risk is therefore no longer simply stagflation. It is policy collision. Europe is increasing defence spending because geopolitical risk has risen. It is investing in energy security because supply chains have become less reliable. It is borrowing more because strategic autonomy costs money. And the ECB is raising rates at the same time because those same geopolitical risks are driving inflation. Europe is paying twice. Once through higher energy prices. Again through higher interest rates. That is why this ECB decision matters beyond 25 basis points. The war in Iran is no longer only influencing oil markets. It is beginning to determine the price of money in Europe. And if the conflict persists, Frankfurt may discover that the next phase of European monetary policy is being written thousands of kilometres away.