A joint research team from the ADD and Seoul National University of Science and Technology calculated an accurate theoretical model, and concluded that adjustment to system configuration was possible without major design changes.

The engineers of the ADD and Dongmyeong Heavy Industries (now Mottrol) found that the noise was due to excessive shaking of hydraulic pressure, thus creating an experimental device using the principle of Helmholtz attenuators used in car mufflers.

Later, during a Data Exchange Agreement meeting, South Korea and the United States confirmed that the U.S. had no claim to any intellectual property rights of the howitzer, to avoid possible disputes in the future.

[14][15] From 1992 to 1993, the developers explored and confirmed the required operational capability, such as the system suitability of major components and the possibility of reaching the maximum firing range of 40 kilometers (25 mi).

The prototypes fired 4,100 rounds and underwent 13,800 kilometers (8,600 mi) of mobility tests including extreme temperature conditions and various type of terrain such as ski courses during the winter season.

[4][38] The main armament is a CN98 155 mm, 52-calibre artillery gun manufactured by Kia Heavy Industry (now Hyundai WIA),[39] with a maximum firing range of 41 kilometers (25 mi) with K307 rounds.

[41] The K9 uses the TALIN (Tactical Advanced Land Inertial Navigator) 5000 for its INS, purchased from Honeywell Aerospace after the announcement of the development of a ring laser gyroscope system that can withstand the shock from gunfire.

[62][63] In 2004, KRCMI (Korea Research Center for Measuring Instruments) developed a Doppler radar calibration system, which significantly increased accuracy by lowering the impact error from 0.1% to 0.05%.

[77] On 20 June 2024, the Republic of Korea Army and Hanwha Aerospace signed an MOU on cooperation and support for the promotion of the Korea-Army International Course (K-AIC), a Korean weapons system curriculum that will begin in July.

On the other hand, Samsung Techwin argued that both the processor and the OS are widely used in the military including newly produced weapons, that older CPUs are more durable, and that DOS has a lower failure rate.

[127] In October at the Korea Army International Defense Industry Exhibition (KADEX) 2024, Hanwha Aerospace showcased a small-scaled model of the K9A3, which no longer resembles external appearance of earlier variants.

[129][130][131][132] The vehicle has a combat weight of 47 metric tons,[133] and can support a K9 team by carrying and resupplying 104 shells of 155 mm artillery ammunition and 504 units of charges under heavy fire.

The vehicle is armed with the K6 HMG-mounted RCWS with the capability to shoot down drones using AI technology, anti-air missile launchers, and additional armor plate for mine protection.

[1] In August 2017, a K9 operated by the 5th Artillery Brigade of the Republic of Korea Army was set ablaze during a firing exercise, causing 3 deaths and 4 wounds among crew members and instructors.

After the investigation, it was found that a faulty spring caused the hammer to detonate prematurely, pushing the explosion into the vehicle before the breech was fully closed, and ignited the additional charges which had been taken out from the rack for the next firing.

The Republic of Korea Armed Forces responded by installing black boxes and an AFSS (automatic fire suppression system), reinforcing maintenance, and providing flame-resistance uniforms to crew members.

Another meeting was held on 4 October between Atilla Ateş, commander of the Turkish Land Forces, and military attaché Colonel Go regarding K9 production in Turkey and solution for import restriction on MTU Friedrichshafen engines by German government.

On 4 May 2000, the Ministry of National Defense of the Republic of Korea and Turkish Land Forces Command signed a memorandum of understanding (MOU) to supply 350 K9 systems till 2011.

On 29 May 2000 during ministerial talks, South Korea asked Germany to permit sales of MTU engines, or it may experience hardship in purchasing German equipment for its future needs.

[166] In December 2014, Samsung Techwin signed a cooperation agreement with Huta Stalowa Wola to supply modified K9 Thunder chassis for AHS Krab self-propelled howitzer.

[172] On 29 May, Polish minister of defense visited South Korea for high level talks regarding the purchase of various Korean weapons including additional K9 chassis to increase AHS Krab production.

[200] On 4 April 2024, Hanwha Aerospace opened a European office in Warsaw and announced the integration of the K9 and Krab howitzer systems with cooperation from HSW to improve the operational and maintenance efficiency of the Polish military.

[220] On 25 March 2012, South Korean president Lee Myung-bak and the Indian Prime Minister, Manmohan Singh signed Memorandum of Understanding (MoU) to strengthen the economy and military exchanges.

[246] In May 2015, Samsung Techwin joined the Norwegian artillery upgrade program, competing against the KMW Panzerhaubitze 2000, the Nexter CAESAR 6x6, and the RUAG M109 KAWEST to replace Norway's M109Gs with 24 new systems.

[1][254] In August 2016, the Norwegian Defence Materiel Agency published their intention to continue negotiations with Hanwha Techwin and RUAG, while Krauss-Maffei Wegmann and Nexter Systems had been put "on hold".

[279] In September 2020, the Minister for Defense, Linda Reynolds, announced a request for tender to locally build 30 K9s under the Land 8116 Phase 1 Protected Mobility Fires requirement.

[306] In the same month, the Egyptian minister of military production visited Hanwha Defense and Hyundai WIA facility to see the manufacturing process of the K9 Thunder and K2 Black Panther respectively.

[316][317] On 22 October 2022, Hanwha Defense signed a contract with Arab International Optronics to transfer automatic fire control system (AFCS) and other substantial technologies.

[328] The contract bid for the tracked systems started on 29 July 2023, and three companies participated: BMC Savunma Sanayi with the T-155 Fırtına, Krauss-Maffei Wegmann with the Panzerhaubitze 2000, and Hanwha with the K9 Thunder.

[334][335] Vietnam People's Army high-ranking officials showed interests in the K9 by visiting ROKA K9 operator unit and having discussion with Hanwha Aerospace on the potential K9 procurement for VPA.