On Sunday, September 22, 1985, the finance ministers of France, West Germany, Japan, the United Kingdom, and the United States met at the Plaza Hotel in New York City. The communiqué they released announced coordinated intervention to weaken the dollar, which had appreciated approximately 50 percent against major currencies between 1980 and 1985 under the Volcker tightening cycle and accumulated US fiscal expansion. James Baker (US Treasury Secretary), Pierre Bérégovoy (France), Gerhard Stoltenberg (Germany), Noboru Takeshita (Japan), and Nigel Lawson (UK) had reached agreement that coordinated dollar weakening was preferable to continued dollar strength. By December 1985, the dollar had fallen approximately 15 percent against the deutsche mark and approximately 19 percent against the yen.

Eighteen months later, on Sunday, February 22, 1987, the same group plus Canada (G6 plus Canada effectively becoming the operative G7 framework) met at the Louvre in Paris. The Louvre Accord communiqué announced that the dollar weakening had gone far enough; coordinated intervention would now stabilize exchange rates around current levels. The framework held through autumn 1987 until the October 19 stock market crash disrupted it. The Plaza-Louvre coordination defined the most ambitious peacetime central bank divergence-management framework in the post-Bretton Woods era.

This Desk has watched divergence frameworks across the four decades since with the patience the historical record demands. The Q3 2026 setup — Fed expected to cut, ECB holding at 2 percent with potential June hike to 2.25 percent, BoJ holding at 0.75 percent with internal pressure to normalize, BoE holding at 4.50 percent with one MPC member voting for cuts — represents the most operationally complex divergence framework since the 1985-1987 episode. Reading the 2026 setup against the Plaza-Louvre experience and against the 1989-1994 Greenspan transition is the analytical exercise.

What Specifically Configures the Q3 2026 Test

The expected Q3 2026 path for major central banks, as priced in markets through early May 2026:

The configuration produces specific currency-level pressures. USD/JPY breaking through 160 in late April 2026 and triggering two interventions (April 30 and May 7) reflects the rate-gap arithmetic — Fed at 3.50-3.75 against BoJ at 0.75 produces 275-300 bp differential supporting yen carry trades.

EUR/USD around 1.08-1.10 reflects the narrowing-but-not-collapsing differential — Fed at 3.625 (midpoint) versus ECB deposit at 2.00 produces 162 bp differential, narrower than 2024 levels.

GBP/USD around 1.26-1.27 reflects relatively narrower differentials and contained UK macro uncertainty — Fed at 3.625 against BoE at 4.50 produces a -88 bp differential (Fed comparatively easier than BoE), supporting modest GBP firmness.

The Q3 2026 stress test arises if any of these configurations breaks. The most likely break paths: Fed signals fewer cuts than priced (dollar strength); BoJ moves to 1.00 (yen sharp move stronger); ECB hikes faster than expected (euro firms); Iran conflict escalation (broader risk-off).

The Plaza Accord: What the Coordination Looked Like

The historical reference requires specific reconstruction. The Plaza Accord did not begin with the September 22 meeting itself — it required preceding institutional groundwork.

Through 1984-1985, the dollar had appreciated to historic levels against major currencies. DXY peaked in February 1985 at approximately 164 (DXY uses a different basket than current; equivalent peak measure was 50 percent above 1980 levels). US current account deficit had widened from approximately 1.5 percent of GDP in 1981 to 3.0 percent by 1985. US manufacturing was struggling against imports. Congressional protectionist pressure was mounting.

The Reagan administration had been formally committed to floating exchange rates through 1981-1984 — Treasury Secretary Donald Regan had been explicit that the US would not coordinate intervention. James Baker's January 1985 move to Treasury changed this framework. By summer 1985, US Treasury was working with G5 partners on coordination.

The September 22 meeting itself ran from morning through afternoon. The communiqué was released after market close in New York. Coordinated intervention began Monday morning. By end-September 1985, intervention had been substantial across all five central banks.

Through Q4 1985:

By end-1985, the dollar had moved approximately 14 percent lower against the DEM and 19 percent lower against the JPY from the Plaza level. The intervention had worked at the targeted scale.

The structural lesson from Plaza: coordinated intervention can move exchange rates against fundamentals at scale when central banks act jointly with explicit communication. The framework requires high-level political agreement that produces and sustains the coordination.

The Louvre Accord: What the Stabilization Looked Like

Eighteen months later, the framework shifted from coordinated weakening to coordinated stabilization.

By February 1987, the dollar had fallen approximately 30 percent against major currencies from its February 1985 peak. The G7 had concerns that further weakening would produce excess inflation in the US and excess disinflation pressure in Japan and Germany. The Louvre meeting agreed on reference ranges (informal, never published) within which exchange rates should be stabilized through coordinated intervention.

The framework held through 1987 until the October 19 crash disrupted it. Specifically:

The structural lesson from Louvre: coordinated stabilization frameworks can hold during normal market conditions but face stress during crisis episodes when central banks face conflicting domestic priorities (Fed needing to cut for equity-market reasons, others needing to maintain rates).

The 1989-1994 Greenspan Transition

A second instructive comparison: the 1989-1994 Fed-ECB-BoJ divergence sequence under Alan Greenspan.

Through 1989-1991, the Fed cut rates aggressively in response to the 1990-1991 recession. By August 1992, the federal funds rate had reached 3 percent, where it would remain for two years. The Bundesbank, dealing with post-reunification inflation, held rates high through 1991-1992 (Lombard rate at 9.75 percent by late 1992). The BoJ, dealing with the early stages of the post-bubble adjustment, was cutting more cautiously than the Fed.

The divergence produced specific FX outcomes:

The 1992 ERM episode is the operative warning. A divergence framework that requires currency-level fixities (such as ERM bands) will break when the underlying rate divergence becomes sustained. The 2026 framework does not have explicit currency-level fixities, but the implicit framework — managed-float regimes with intervention readiness — has its own break points.

What 2026 Specifically Inherits and What Differs

Three structural inheritances from the Plaza-Louvre and Greenspan-transition episodes operate in the 2026 framework.

First, the divergence-tolerable threshold. Plaza demonstrated that 50 percent dollar appreciation produces unsustainable adjustment pressure. Louvre demonstrated that 30 percent dollar depreciation tests the limits in the other direction. The 2026 dollar at DXY 99 sits well within the historically tolerable range. The current divergence is not yet at Plaza-scale stress.

Second, the political-coordination unavailability. The 2026 framework specifically lacks the political coordination Plaza-Louvre had. There is no current G7 framework explicitly coordinating intervention. The Mar-a-Lago accord rumors that circulated in early 2026 produced no coordinated framework. Each central bank operates within its domestic mandate and uses unilateral intervention when needed.

Third, the institutional-memory effect. Central bankers in 2026 are personally aware of Plaza-Louvre, the 1992 ERM episode, the 1995 yen-rally that included reverse-coordination at 79.75, the 2008 swap-line activations, and the 2024-2026 yen interventions. The institutional response framework is sophisticated. What it lacks is political mandate to engage in coordinated frameworks at Plaza scale.

What 2026 does not inherit cleanly: the assumption of fundamental cooperation. The 1985 Plaza coordination depended on shared assumption that a strong dollar was creating systemic problems requiring multilateral solution. The 2026 framework operates in a different political environment where US trade policy and bilateral rather than multilateral framings dominate.

The Q3 Stress Test Scenarios

Three scenarios that could test the divergence framework through Q3 2026.

Scenario A: BoJ moves to 1.00 percent in July. If the dissenters at the April 30 meeting capture the consensus by July, the rate gap to the Fed compresses. USD/JPY would likely retest 152-155. Yen-funded carry positioning unwinds. The BoJ's path becomes the operationally interesting variable.

Scenario B: ECB hikes to 2.25 in June. If energy-driven inflation persists and the Council moves pre-emptively, EUR/USD firms sharply. The narrowing Fed-ECB differential supports euro strength. DXY weakens earlier than the H2 forecast track.

Scenario C: Iran conflict escalation produces broader risk-off. A material military escalation produces dollar safe-haven strength, oil price spike, and broader EM currency pressure. The framework operates around the shock rather than the underlying divergence.

The probability-weighted base case is that the framework holds through Q3 with modest adjustments. The tail risks reflect specific event paths rather than framework collapse.

What This Desk Tracks Through Q2-Q3 2026

Three datapoints across the rest of 2026 against the framework.

The June FOMC and ECB meetings, specifically guidance shifts. If the dot-plot stays at one cut and ECB signals June 4-5 hike, the divergence configuration shifts modestly. Material guidance shifts in either direction would produce market repricing.

The June and July BoJ Policy Board votes. The 6-3 split at April 30 will be the reference. Dissenters gaining ground (5-4) signals consensus shift toward normalization. Dissenters losing ground (7-2 or unanimous) signals consensus stability.

Iran conflict trajectory and oil prices. Brent at $93 through April could move toward $80 (resolution path) or $110+ (escalation path). The energy variable affects all four major central banks simultaneously and is the dominant external variable.

Honest Limits

This Desk reads the historical record from publicly available G7 communiqués, Federal Reserve archives, BIS quarterly reviews, and substantial economic literature on the Plaza-Louvre period and Greenspan transition. The 2026 figures cited reflect Reuters, Bloomberg, ECB, BoJ, and Federal Reserve data through early May 2026. Specific scenarios reflect conditional reasoning rather than forecasts. FX positioning carries substantial risk; specific household and institutional decisions warrant qualified consultation.

Sources