President-elect Donald Trump will return to office on Monday having promised a peace deal to end Russia's war on Ukraine, still raging after nearly three years of combat.

The partnership, according to officials who spoke to ABC News, has been essential to Ukraine defending itself as Russia invaded almost three years ago.

ABC News' Patrick Reevell on the secret partnership between the U.S. & Ukraine and how it has been crucial in helping the country defend itself against Russia.

British Prime Minister Keir Starmer has arrived in Ukraine's capital with a pledge to help guarantee the country’s security for a century, days before Donald Trump is to be sworn in as U.S. president

Ukrainian President Volodymyr Zelenskyy warned allies that the defense of his nation is a litmus test for broader Western resolve.

Ukrainian President Volodymyr Zelenskyy is visiting Poland after the two countries reached an agreement on a longstanding source of tensions between them: the exhumation of Polish victims of World War II-era massacres by Ukrainian nationalists

"We also agreed to work closely with key allies on achieving peace and developing effective security guarantees," Ukrainian President Volodymyr Zelenskyy added.

The players were chosen from among the thousands of Ukrainians wounded in the war

Ukrainian President Volodymyr Zelenskyy predicted that his nation's forces would "undoubtedly" capture more North Korean troops.

President Volodymyr Zelenskyy says Ukraine's forces have captured two North Korean soldiers fighting alongside Russian troops in Russia’s Kursk border region

Ukrainian President Volodymyr Zelenskyy and U_S_ Defense Secretary Lloyd Austin used their final meeting in Germany to press the incoming Trump administration to not give up on Kyiv’s fight, warning that to cease military support now “will only invite ...

Ukrainian President Volodymyr Zelenskyy said that some 38,000 Russian troops have been killed or wounded fighting in Russia's western Kursk region since August.

Ukrainian forces on Sunday launched a new offensive inside Russia's western Kursk border region, going on the attack with substantial forces.

French President Emmanuel Macron extended an olive branch to U.S. President-elect Donald Trump on Monday, declaring that France is “a solid ally” as he outlined his vision for global diplomacy in 2025

Ukraine appears to be going on the offensive against Russia, attempting to seize more territory inside the Kursk region of Russia, the same region where Ukraine mounted a major offensive in August.

Ukrainian President Volodymyr Zelenskyy says he will urge allies to boost his country's air defenses at a meeting this week in Germany

George Stephanopoulos interviews Rep. Michael McCaul, R-Texas, on “This Week.”

Russia-appointed officials in Moscow-occupied Crimea have announced a regional emergency after oil was detected on the coast of Sevastopol

Ukrainian President Volodymyr Zelenskyy says U.S. President-elect Donald Trump is “strong and unpredictable” and those qualities can be a decisive factor in his policy approach to Russia’s invasion of Ukraine

At least six people were injured in Kyiv as Russia launched a drone strike on the capital in the early hours of Wednesday, city officials said.

"We stopped the transit of Russian gas, this is a historic event," Herman Galushchenko, Ukraine's energy minister, said in a statement.

"At my direction, the United States will continue to work relentlessly to strengthen Ukraine's position in this war over the remainder of my time in office," President Joe Biden said.

The United States "will continue to work relentlessly to strengthen Ukraine's position in this war over the remainder of my time in office," Biden said.

ABC News’ Jonathan Karl interviews Sen. Ben Cardin, D-Md., on “This Week.”

Ukrainian special forces have released several excerpts from a purported diary it said was found on a North Korean soldier killed in front-line fighting in Russia.

Ukrainians faced fresh Russian drone and missile strikes on energy infrastructure nationwide on Tuesday night into Christmas Day morning.

Ukrainians faced fresh Russian drone and missile strikes on energy infrastructure nationwide on Tuesday night into Christmas Day morning.

Ukrainian President Volodymyr Zelenskyy said more than 3,000 North Korean soldiers have been killed or wounded fighting for Moscow in Russia's western Kursk region.

Two Russian airports were put under flight restrictions early Saturday after authorities alleged an attack by Ukrainian drones, according to state-run news agencies.

A Russian missile strike killed one person and wounded seven others early on Friday morning, Ukraine's Ministry of Defense said.

North Korea may dispatch more troops to Russia despite casualties, South Korea’s National Intelligence told lawmakers during a briefing Thursday.

A senior Russian general was killed in a bomb blast in a residential neighborhood in Moscow, Russian media reported early Tuesday.

Ukraine's intelligence services released new information Tuesday about the conduct of North Korean troops now fighting alongside Russian forces in the Kursk region.

Dashcam video shows the moment a bomb hidden on scooter detonated, killing Lt. Gen. Igor Kirillov and his aide. Ukraine called Kirillov a war criminal, while Russia called the attack terrorism.

A senior Russian general was killed in a bomb blast in a residential neighborhood in Moscow, Russian media reported early Tuesday.

Lt. Gen. Igor Kirillov, the head of Russia's radiation, chemical and biological protection troops, was killed by a hidden explosive in what Ukrainian sources told ABC News was an intelligence operation.

ABC News’ Ian Pannell and ABC News contributor Mick Mulroy discuss the death of Lt. Gen. Igor Kirillov, a senior Russian general who was killed in a bomb blast in a residential neighborhood in Moscow.

The Ukrainian Defense Ministry's Main Directorate of Intelligence said on Monday that at least 30 North Korean soldiers were killed and wounded in weekend battles.

Russia launched a massive aerial attack against Ukraine, firing 93 cruise and ballistic missiles and almost 200 drones, Ukrainian President Volodymyr Zelenskyy said. ABC News’ Marcus Moore reports.

Nobel Laureate Oleksandra Matviichuk discusses her work exposing underreported stories of the war in Ukraine and Russian's aggression.

Nobel Laureate Oleksandra Matviichuk on her work exposing hidden and underreported stories of the war in Ukraine.

Lloyd Austin announced the Pentagon will send nearly $1 billion to Ukraine, bringing the total the United States has committed to Ukraine to more than $62 billion.

Ukrainian President Volodymyr Zelenskyy announced sanctions on 19 members of the Georgian government, who he accused of "surrendering" the country to Russian control.

Belarusian President Alexander Lukashenko thus far appears to have kept his nation out of the worst of the spiraling war engulfing his neighbors to the east and south.

Kremlin spokesperson Dmitry Peskov told the Izvestia newspaper in an interview published Wednesday that Russia sees "no grounds for negotiations yet" to end Moscow's war.

The $725 million in military assistance, will include counter-drone systems and munitions for its High Mobility Artillery Rocket System.

Ukraine's air force said it shot down 22 of 28 Russian drones in Moscow's overnight barrage, though acknowledged "several hits on critical infrastructure facilities."

Ukraine's air force said it recorded 110 Russian attack drones launched into the country overnight into Sunday morning.

ABC News’ Jonathan Karl interviews White House National Security Adviser Jake Sullivan on “This Week.”

National Security Adviser Jake Sullivan said President Joe Biden is looking to make as much progress as possible on foreign policy before he leaves office next month.