It was hit by long-term Russian partner Gazprom withholding gas exports after Moscow's invasion of Ukraine.

Uniper had to buy gas at higher prices on the spot market to fulfil supply contracts with smaller utilities and industry, forcing Berlin to agree in September to nationalise it.

Below is a chronology of the crisis:

DECEMBER

DEC. 19 - Uniper shareholders vote on the bailout at an extraordinary shareholder meeting.

DEC. 16 - The European Commission approved Uniper's acquisition by the German government under competition laws, still leaving approval needed under state aid rules, which is expected to be tied to conditions.

NOVEMBER

NOV. 30 - Uniper launched an arbitration process in the hope of securing billions of euros in compensation from Russia's Gazprom over undelivered gas volumes.

NOV. 23 - Uniper said it needed 25 billion euros more from Berlin and that it would ask shareholders for approval of the stabilisation package.

OCTOBER

After Uniper received pledges of more than 29 billion euros in September, it was becoming clear that tens of billions of euros more could be needed to survive the European gas crisis and keep up purchases, sources said.

Part of the support came from a 200 billion euro government support programme for energy hardship, which will also support peers Sefe and EnBW's VNG.

SEPTEMBER

Under a nationalisation plan, Germany said it will hold 99% of Uniper once it completes a capital increase and buys the holding of Finnish parent Fortum.

The reasons cited were that the move will prevent gas rationing, chaos in the market and job losses at Uniper.

Uniper was said to be considering proceedings against Gazprom over the gas supply cuts in a Swedish court.

AUGUST

Uniper reported a 12.3 billion euro loss in the first half and withdrew its 2022 outlook.

JULY

The German government agreed to a 15 billion euro rescue deal and to more than quadruple a credit line with state-lender KfW.

JUNE

Uniper withdrew 2022 outlook and calls for a bailout.

MAY

Uniper implemented Moscow's demand to pay for gas in roubles.

APRIL

Uniper posted impairments related to its Russian generation unit.

MARCH

Uniper signalled exit from Russia.

FEBRUARY

Uniper proposed a 95% cut in its 2021 dividend.

The Nord Stream 2 pipeline link in which it was a co-financier, is abandoned, leaving Uniper with a 1 billion euro write-down.

Russia on Feb. 24 invades Ukraine, calling it a "special military operation".

JANUARY

Uniper secures credit facilities worth 10 billion euros from Fortum and German state bank KfW plus 1.8 billion euros in bank loans to address high prices and volatility.

2021

Global gas markets become tight in a post-COVID recovery and Russia starts sending lower exports westwards, pointing to the imminent start of the Nord Stream 2 pipeline.

Uniper holds on to view that Russia is a reliable shipper.

LEGACY

Uniper represents the legacy business of Ruhrgas that E.ON took over in 2003 and fully absorbed in 2013.

The purchase, which cemented joint German-Russian trade and oil and gas exploration links, was opposed by the cartel office and by some as pandering to pro-Moscow interests.

E.ON spun off a majority of Uniper in 2016 and later agreed to sell its remaining stake to Fortum.

($1 = 0.9408 euros)

(Reporting by Vera Eckert; Editing by Miranda Murray, Barbara Lewis and Alexander Smith)