Between 1938 and 1950, it was a credit union whose purpose was to provide tradesmen and artisans loans on favourable terms to promote economic growth in Turkey.

Halkbank absorbed several smaller-sized failed state banks in the 1990s and early 2000s: Töbank in 1992, Sümerbank in 1993, Etibank in 1998 and Emlakbank in 2001.

[7] Halkbank seems, between March 2012 and July 2013 while the UN sanctions regime was in place prior to the November 2013 P5+1 agreement, to have purchased some $13bn worth of gold on the open market.

[7] In defending its decision not to enforce its own sanctions, the Obama administration insisted that Turkey only transferred gold to private Iranian citizens.

"[7] In December 2013, Halkbank's CEO Süleyman Aslan was arrested and charged with taking bribes[9] from, among others, Reza Zarrab, an Iranian-Azeri businessman who had taken Turkish citizenship under the name Sarraf.

"[7] In March 2017, deputy head of the bank Mehmet Hakan Atilla was arrested[12] by the U.S. government for conspiring to evade sanctions against Iran by helping Zarrab "use U.S. financial institutions to engage in prohibited financial transactions that illegally funneled millions of dollars to Iran".

[14] In Ankara in March 2017, U.S. Secretary of State Rex Tillerson said there was no link between the Turkish request for extradition of Gülen and the arrest of Atilla and that both cases would proceed in conformity with the law.

[12] Atilla's trial commenced in New York City federal court in November 2017, with Zarrab agreeing to testify after reaching a plea deal with prosecutors.

Erdoğan has sought, unsuccessfully, to persuade American officials to drop the case, and the state media has been downplaying coverage of the trial.

[21] In 2016, President Erdoğan asked then-Vice-President Joe Biden to remove Preet Bharara, the U.S. attorney for the Southern District of New York who would go on to indict Zarrab.

[17] Following continued lobbying by President Erdoğan, Donald Trump did fire Bharara in 2017, and eventually replaced him with Geoffrey Berman.

[17] In late 2018, President Erdoğan personally lobbied President Trump to drop further investigations into Halkbank, once in person during the G20 meeting in Buenos Aires (1 November 2018), and once on a phone call (14 December 2018); according to John Bolton, a first-hand witness of both events, Trump then agreed to have the investigations dropped.

[17] On 14 December 2018, the Department of Justice, then headed by Matthew Whitaker, notified Berman's office, that it would become more involved in the Halkbank investigation.