Ukraine–Russia War: Probability of Ending Before October 1, 2026

Updated September 21, 2026

Event Definition

The event resolves positively if, before October 1, 2026, one of the following occurs:

Russia and Ukraine sign a peace treaty, armistice, or other qualifying written agreement that ends the broader war;
Russia annexes all or most of Ukraine; or
Ukraine wins the war in a manner that changes the authorities governing the Kremlin.

A temporary humanitarian pause, prisoner exchange, diplomatic meeting, political declaration, energy-only truce, maritime arrangement, or agreement merely to resume negotiations would not normally qualify unless the text clearly ends active hostilities across the broader conflict.

As of September 21, 2026, there are 10 calendar days—September 21 through September 30, inclusive—before the October 1 resolution date. The remaining window is therefore exceptionally short.

1. Executive Forecast

Estimated probability of a qualifying event before October 1, 2026: approximately 0.2–0.5%

Central estimate: approximately 0.3%.

The probability has increased modestly from the previous central estimate of approximately 0.2%, primarily because President Volodymyr Zelenskyy and President Donald Trump have now agreed to meet in New York during the UN General Assembly. Ukraine’s government says the meeting could address de-escalation measures, energy and food security, and broader security issues. (president.gov.ua)

However, the new diplomatic development is counterbalanced by exceptionally negative military evidence:

Ukraine conducted what was described as its largest-ever drone attack against Moscow and surrounding areas;
Russia threatened to intensify strikes against Kyiv;
Russian and Ukrainian long-range attacks are continuing at a high level;
the purported energy ceasefire remains unconfirmed and conditional;
no Russia–Ukraine signing process or nationwide ceasefire mechanism has been announced; and
only 10 days remain.

The Trump–Zelenskyy meeting creates a plausible venue for a last-minute diplomatic initiative, but it is not itself evidence that Russia has accepted the terms necessary for a war-ending agreement. Current reporting indicates that the United States is attempting to reduce the remaining negotiating obstacles to “one or two” major issues, but those issues appear to include fundamental security and territorial questions rather than merely technical implementation details. (axios.com)

Updated probability table

Outcome before October 1, 2026	Estimated probability
Qualifying peace treaty, armistice, or war-ending written agreement	0.2–0.5%
Russian annexation of all or most of Ukraine	Far below 0.1%
Ukrainian victory involving a change in Kremlin authorities	Far below 0.1%
War continues without a qualifying settlement	Approximately 99.5–99.8%

The positive probability remains overwhelmingly concentrated in a sudden, U.S.-brokered written armistice. Russian annexation of most or all of Ukraine and a Ukrainian victory involving a change in Kremlin authorities remain effectively implausible within the remaining 10 days.

2. Important Developments Since the September 20 Assessment

2.1 Trump and Zelenskyy have agreed to meet in New York

The most important positive development is that Zelenskyy and Trump have now agreed to meet during the UN General Assembly in New York. Zelenskyy said after a September 20 phone call that the meeting “could change a lot” and that there was diplomatic momentum. The Ukrainian presidential office described the peace process as the government’s top priority and said the discussions could involve de-escalation steps, energy security, food security, and protection of human life. (president.gov.ua)

This is materially more significant than the previous situation, when the meeting was merely being arranged and was not clearly present on the published U.S. schedule. The meeting gives Washington and Kyiv a fixed, high-level diplomatic opportunity before the deadline.

Nevertheless, several limitations remain:

it is a U.S.–Ukraine meeting, not a Russia–Ukraine signing conference;
Russia has not been reported as agreeing to attend a trilateral summit in New York;
the meeting has not produced a public ceasefire text;
the key Russian–Ukrainian disputes remain unresolved; and
even an agreement between Trump and Zelenskyy would require Moscow’s acceptance and implementation.

The meeting therefore raises the short-term probability of a diplomatic announcement or a partial ceasefire more than it raises the probability of a qualifying end to the war.

2.2 Negotiators reportedly see only one or two major obstacles—but they may be fundamental

Ukrainian National Security and Defense Council Secretary Rustem Umerov reportedly said that the number of negotiating obstacles had been reduced from dozens to “essentially one or two” key issues. This suggests that the U.S.-led process may have achieved some progress since the September 6 meetings involving American representatives and Ukrainian officials. (axios.com)

This is positive evidence, but it must be interpreted cautiously. A small number of remaining issues can still be decisive if they concern:

the status of occupied territory;
security guarantees for Ukraine;
the line of contact and military withdrawals;
sanctions relief;
the sequencing of a ceasefire and political negotiations; or
Russia’s demand for recognition of territorial claims.

A negotiation can be close in procedural terms while remaining far from agreement on its central substance. The available reporting does not establish that Russia has accepted a nationwide ceasefire on terms Kyiv could sign.

2.3 Military escalation has sharply intensified

On September 20, Ukraine launched more than 1,000 drones toward Russia, including hundreds directed at Moscow. Russian authorities described the attack as the largest of the war against the capital region. At least two people were reportedly killed, and an oil facility was set alight. Russia’s Defense Ministry said it would continue and intensify strikes against military targets in Kyiv. (apnews.com)

The timing is particularly negative for the event. The attack occurred immediately before the UN diplomatic window and during the final day of Russia’s parliamentary election. Rather than showing an operational transition toward a ceasefire, the episode demonstrates that both sides retain the willingness and capability to conduct large-scale attacks deep behind the front.

The escalation does not make a subsequent agreement impossible. Governments sometimes negotiate while fighting intensifies, particularly when attacks are intended to improve bargaining leverage. But it makes an imminent, mutually trusted cessation of hostilities less likely, especially because Russia has publicly threatened retaliatory escalation.

2.4 Russia’s parliamentary election reinforces political continuity

Early results from Russia’s parliamentary election showed the Kremlin-aligned United Russia party dominating a tightly controlled vote. The election included voting in Ukrainian territories that Russia claims to have annexed but does not fully control. (apnews.com)

This provides no evidence of a leadership crisis, succession struggle, coup, or political rupture in Moscow. It also reinforces Russia’s continuing institutionalization of its territorial claims.

The election may still be followed by a diplomatic initiative intended to demonstrate strength or seek sanctions relief. However, the available evidence points toward continuity under Putin rather than a change in Kremlin authorities. The “Ukrainian victory through a change in Kremlin authorities” branch of the event remains extraordinarily unlikely before October 1.

2.5 The U.S. sanctions bill has become law

President Trump signed the Graham sanctions bill on September 18. The legislation increases Washington’s ability to impose pressure on Russian officials, financial institutions, energy interests, and sanctions-evasion networks. Zelenskyy thanked Trump for signing it and described it as important to the peace effort. (investing.com)

The law may improve the United States’ negotiating leverage over Moscow. In the immediate 10-day window, however, its effect is ambiguous:

it could increase Russia’s incentive to seek a settlement;
it could make Moscow more resistant to concessions under pressure;
implementation and economic effects may take longer than the remaining deadline; and
sanctions relief would likely become part of any serious negotiation.

The sanctions law is therefore a medium-term pressure instrument rather than evidence of an imminent settlement.

2.6 The purported energy truce remains conditional and incomplete

Trump previously stated that Russia and Ukraine had agreed not to strike each other’s energy infrastructure. Kyiv has not treated that statement as an operational bilateral agreement. Zelenskyy’s position is that Ukraine could halt attacks on Russian critical infrastructure if Russia genuinely stops striking Ukrainian energy and other critical facilities. Ukrainian officials have also indicated that the specific facilities and terms still need to be defined. (apnews.com)

No publicly confirmed joint document has established:

the facilities covered;
the exact start time;
the duration;
monitoring arrangements;
attribution procedures;
enforcement mechanisms; or
consequences for violations.

Even if finalized, an energy-only truce would not normally resolve the event while ground combat, attacks on military targets, missile strikes, and drone operations continued.

3. Current Diplomatic and Military Situation

United States

The Trump administration remains the principal external actor attempting to move Moscow and Kyiv toward de-escalation. U.S. representatives Steve Witkoff and Jared Kushner have met with Russian and Ukrainian officials, and the administration is pursuing reciprocal measures involving infrastructure, winter de-escalation, and renewed negotiations. (axios.com)

The newly confirmed Trump–Zelenskyy meeting improves the possibility of a concrete proposal before the deadline. The administration may attempt to:

formalize an energy-infrastructure truce;
add maritime or Black Sea restrictions;
secure a broader temporary ceasefire;
restart trilateral negotiations; or
produce a framework for a later comprehensive settlement.

The major uncertainty is whether Washington can obtain Russian agreement quickly enough. There is no current evidence that Moscow has accepted the terms of a nationwide armistice.

Russia

Russia continues to maintain the diplomatic channel but is combining negotiations with military pressure. Its response to the Ukrainian drone attack was to threaten intensified strikes against Kyiv. The Kremlin’s election also continues to frame occupied Ukrainian territories as part of Russia. (apnews.com)

Russia has not publicly accepted:

an unconditional nationwide ceasefire;
a freeze along the current line of contact;
binding security guarantees for Ukraine;
postponement of territorial-status questions on terms acceptable to Kyiv; or
a comprehensive halt to missile, drone, and ground operations.

Moscow’s conduct remains more consistent with coercive bargaining than with preparation for an immediate settlement.

Ukraine

Ukraine remains diplomatically engaged and appears willing to consider reciprocal de-escalation measures. Zelenskyy’s office has emphasized energy security, food security, and protection of civilians, and Umerov has suggested that the remaining negotiating obstacles may have narrowed substantially. (president.gov.ua)

At the same time, Ukraine continues long-range strikes against Russian military and energy-related targets. Kyiv’s large September 20 drone attack demonstrates that Ukraine is still using military pressure while diplomacy proceeds.

Ukraine is unlikely to accept a settlement requiring immediate recognition of Russian annexations or a one-sided cessation that leaves Russia free to continue attacking. This creates a narrow space for an interim armistice: the agreement would likely need to stop broad hostilities while postponing the final territorial question.

Battlefield activity

The war remains fully active across multiple domains:

Russian missile and drone strikes continue against Ukrainian cities and infrastructure;
Ukraine continues attacks against Russian oil, military, and logistical targets;
Russia has threatened to intensify strikes following the latest attack on Moscow;
no verified nationwide stand-down exists; and
the parties have not announced a jointly monitored ceasefire.

The military picture is therefore still inconsistent with a war that is already ending.

4. Evidence Supporting a Positive Resolution

4.1 A leader-level Trump–Zelenskyy meeting is now agreed

The scheduled meeting creates the clearest remaining diplomatic opportunity before October 1. It could allow the United States and Ukraine to settle Kyiv’s position on a proposed armistice and produce a public initiative directed at Moscow. (president.gov.ua)

4.2 U.S.-led talks may have narrowed the negotiating agenda

The reported reduction of the obstacles from dozens to one or two suggests some progress in the recent U.S.-Ukraine discussions. If the remaining issues are primarily sequencing, monitoring, or implementation questions, a short-term armistice remains conceivable. (axios.com)

4.3 An interim armistice could avoid resolving sovereignty immediately

A qualifying written agreement need not necessarily be a final peace treaty. A possible arrangement could:

halt nationwide missile, drone, and ground attacks;
freeze military positions;
establish monitoring;
protect energy, food, and civilian infrastructure;
provide for prisoner exchanges;
postpone territorial-status questions; and
establish later negotiations on sovereignty and security guarantees.

That type of agreement is diplomatically more achievable than a final peace treaty, although there is no public evidence that Russia and Ukraine have reached this level of convergence.

4.4 Sanctions may increase Moscow’s incentive to negotiate

The new U.S. sanctions law increases potential costs for Russia and gives Washington additional leverage. If Trump signals that sanctions relief could accompany a ceasefire, Moscow may have greater incentive to consider a temporary agreement. (apnews.com)

This is a possible future catalyst, but it is not yet an observable settlement process.

5. Evidence Against a Positive Resolution

5.1 Hostilities have intensified rather than declined

The largest reported Ukrainian drone attack on Moscow, Russia’s threat to intensify attacks on Kyiv, and continuing Russian strikes all indicate that the parties have not entered an operational de-escalation phase. (apnews.com)

5.2 The energy proposal is not a war-ending agreement

Even if Russia and Ukraine formalize an energy truce, it would leave unresolved:

ground combat;
attacks on military facilities;
strikes against oil and defense infrastructure;
maritime and port operations;
territorial claims; and
the broader front line.

It would therefore be a confidence-building measure, not necessarily a qualifying settlement.

5.3 The new Trump–Zelenskyy meeting is not a Russia–Ukraine agreement

The meeting improves diplomatic prospects but does not show that Russia has accepted a ceasefire. A sequence involving Washington and Kyiv would still require:

agreement on a specific text;
Russian acceptance;
signature or formal adoption by Russia and Ukraine;
military orders to halt operations; and
implementation before September 30.

Completing all five steps in 10 days remains highly unlikely.

5.4 Territorial and security issues remain fundamental

The election in occupied Ukrainian territories and Russia’s continued military activity show that Moscow has not abandoned its territorial claims. Ukraine has likewise not accepted their legal recognition. The remaining “one or two” obstacles may therefore be the most difficult issues in the entire negotiation. (apnews.com)

5.5 The sanctions law may increase pressure without producing immediate compromise

Sanctions can create bargaining leverage, but they can also harden positions. Russia may seek relief as a condition for a settlement, while Ukraine and the United States may insist that relief follow verified compliance. Resolving that sequencing problem before October 1 is unlikely.

5.6 The deadline is now only 10 days away

The parties would need to negotiate, draft, approve, sign, and begin implementing an agreement before October 1. A short political announcement is feasible. A broad, operational agreement ending active hostilities is much more difficult.

5.7 Military collapse scenarios remain implausible

There is no credible evidence that Russia can annex most or all of Ukraine within 10 days, nor that Ukraine can defeat Russia or cause a change in Kremlin authorities during that period. Those branches contribute effectively nothing to the forecast.

6. Scenario Analysis

Scenario A: Written nationwide armistice before October 1

Estimated probability: 0.2–0.5%

Trump and Zelenskyy use their New York meeting to agree on a U.S.-backed proposal. Russia accepts a written nationwide ceasefire, perhaps freezing the front and postponing territorial negotiations.

This is the only realistic positive pathway, but it remains highly unlikely because:

Russia has not accepted the arrangement publicly;
attacks are escalating;
the energy truce is not operational;
territorial and security questions remain unresolved;
no Russian–Ukrainian signing process has been announced; and
only 10 days remain.

Scenario B: Energy, maritime, or infrastructure truce without ending the war

Estimated probability: 15–25%

The Trump–Zelenskyy meeting produces a more detailed energy or maritime agreement, possibly followed by Russian participation or a U.S.-announced framework.

This scenario has become somewhat more plausible because the leader-level meeting is now agreed. It still would not normally satisfy the event unless it clearly expanded into a broader cessation of hostilities.

Scenario C: Diplomatic announcement without an operational ceasefire

Estimated probability: 30–40%

Trump and Zelenskyy announce progress, a framework, or a plan to resume talks. Washington may claim that the parties are close to an agreement, while Russia and Ukraine continue fighting or disagree over implementation.

This is now more likely than before because the meeting is confirmed. It remains much more likely than a qualifying settlement.

Scenario D: Continued fighting with limited diplomatic contact

Estimated probability: 55–70%

The leaders meet, but no operational nationwide agreement results. Russia and Ukraine continue long-range strikes while the United States pursues partial infrastructure measures and negotiations beyond the deadline.

This remains the base case, supported by:

the latest escalation in drone and missile attacks;
Russia’s threat to intensify strikes;
the absence of a verified ceasefire;
unresolved territorial questions;
the lack of Russian participation in a confirmed signing process; and
the extremely short remaining window.

Scenario E: Decisive military or political collapse

Estimated probability: far below 0.1%

This includes Russian annexation of most or all of Ukraine, collapse of the Ukrainian state, or a Ukrainian victory that changes Kremlin authorities.

There is no credible evidence that any such event could occur before October 1.

7. Indicators That Would Materially Increase the Forecast

The probability should rise substantially if any of the following occur:

Russia and Ukraine publish a signed nationwide ceasefire or armistice.
Putin publicly accepts a ceasefire along the current line of contact.
A Trump–Putin–Zelenskyy summit is scheduled before September 30.
Russia accepts postponement of territorial-status questions.
A detailed joint Russian–Ukrainian energy truce is published.
The energy or maritime truce expands to cover ground, missile, and drone operations.
A monitoring and enforcement mechanism is announced.
Russian and Ukrainian attacks decline sharply for several consecutive days.
Moscow and Kyiv agree on a start time and consequences for violations.
Trump and Zelenskyy announce a specific armistice text rather than general diplomatic momentum.
Russia accepts sanctions-relief sequencing linked to verified compliance.
The Kremlin shows an unexpected leadership crisis or rupture.

The forecast should fall toward or below 0.1–0.2% if:

the Trump–Zelenskyy meeting is canceled;
Russia rejects the resulting proposal;
attacks intensify further after the UN meeting;
Moscow reiterates that territorial concessions must precede any ceasefire;
Kyiv rejects a U.S.-backed proposal requiring territorial concessions; or
negotiations are explicitly deferred until October or later.

8. Final Assessment

The latest information modestly improves the probability of a qualifying settlement, but not enough to change the basic conclusion that the event is extremely unlikely.

The principal positive development is the agreement for Trump and Zelenskyy to meet in New York during the UN General Assembly. Ukraine says the meeting may address de-escalation, energy and food security, and fundamental security questions. U.S.-Ukraine discussions have reportedly reduced the number of negotiating obstacles, and Washington continues to seek reciprocal steps that could restart broader negotiations. (president.gov.ua)

The strongest negative evidence is that military activity has escalated sharply. Ukraine conducted a massive drone attack against Moscow, Russia threatened to intensify attacks on Kyiv, and neither side has implemented a verified nationwide ceasefire. The purported energy truce remains conditional and lacks a publicly confirmed text, monitoring system, or enforcement mechanism. (apnews.com)

A leader-level U.S.–Ukraine meeting could produce a diplomatic framework, an energy or maritime truce, or a proposal for a broader armistice. Those outcomes are increasingly plausible. But they would not necessarily satisfy the event. The event requires a written agreement that clearly ends broad active hostilities, Russian annexation of most or all of Ukraine, or a Ukrainian victory involving a change in Kremlin authorities.

Final forecast

Estimated probability that the Ukraine–Russia war ends through a qualifying peace treaty, armistice, settlement, Russian annexation of Ukraine, or Ukrainian victory involving a change in Kremlin authorities before October 1, 2026: approximately 0.2–0.5%, with a central estimate near 0.3%.

The most likely outcome remains that the war continues beyond October 1, 2026, even if Trump and Zelenskyy announce renewed diplomatic progress or a limited infrastructure and maritime arrangement. A last-minute nationwide armistice is possible, but current evidence shows no verified transition from exploratory diplomacy to a jointly accepted, monitored, and operational cessation of hostilities.

Source Document for Event 2 (21-09-2026)