The US and Japan are not trying to fix the Japanese economy's fundamental problems. Instead, they are artificially propping up the yen to ensure the unwinding of the carry trade is a slow, managed decline rather than a sudden, catastrophic collapse that would devastate the global economy.

Any strength in the Euro from a hawkish European Central Bank is unlikely to last. The Eurozone's weak fundamentals—lagging growth, poor equity returns versus the US, and energy price vulnerability—mean that higher interest rates would further stifle the economy, making any rate-driven rally unsustainable and positioning the Euro as a funding currency.

Interventions can temporarily scare investors out of positions but are not a sustainable solution. Without a subsequent shift in domestic monetary policy, such as the Bank of Japan hiking interest rates, the original pressures causing currency weakness will inevitably re-emerge.

Japanese authorities will likely cap the size of any currency intervention to avoid creating a perception of dwindling FX reserves. This strategic limitation means intervention is unlikely to be large enough to halt the Yen's fundamental downtrend driven by Fed hikes.

The Euro was created with monetary union first, assuming political and fiscal union would follow; they haven't. Now, with nationalist governments rising across Europe, the project's core conflict is exposed. A shared currency managed by inwardly-focused national interests is a fundamentally unstable structure.

A government's repeated efforts to defend its currency paradoxically weaken it. Each intervention signals to the market that the country is in economic trouble, eroding investor confidence and creating a self-reinforcing downward spiral. The only sustainable defense is not intervention, but genuine, underlying economic growth and structural reform.

Markets often over-focus on relative interest rate policy when analyzing currencies. During an energy crisis, the macroeconomic effect of rising oil prices is a far more powerful driver. The disproportionate negative impact on energy-importing economies like Japan and Europe will weigh on their currencies more than any central bank actions.

Facing similar demographic and deflationary pressures as Japan a decade ago, Europe will be forced to debase the Euro. This is the only remaining viable policy tool to stimulate tax growth faster than social spending obligations.

Beyond immediate geopolitical pressures, a key structural weakness for the Euro was highlighted at the IMF meetings. The lack of a single, unified capital market in Europe limits its ability to scale up critical spending (like defense) and prevents the Euro from acting as a viable reserve currency alternative to the US dollar.