[10] The design of the Type 218SG was jointly created by Defence Science and Technology Agency (DSTA), ThyssenKrupp Marine Systems (TKMS) and the Republic of Singapore Navy (RSN).

[14] The Type 218SG features several unique characteristics, such as: Current details about the Type 218SG's armament are scant and almost non-existent; however, it is understood that the submarine features eight 533-millimetre (21.0 in) and two 650-millimetre (26 in) forward-firing torpedo tubes— (same configuration with Israel's Dolphin-II submarines) which may be used for firing heavyweight torpedoes, anti-ship missiles and for laying naval mines, as well as a dedicated horizontal air-lock, to disembark naval special forces teams.

[28][29] On 29 November 2013, MINDEF officially contracted TKMS to supply two Type 218SG submarines, along with a training and logistics package, at an estimated cost of US$1.36 billion.

[40] The first submarine, christened as the Invincible, was launched in an elaborate ceremony on 18 February 2019, with defense minister Ng Eng Hen and representatives of the RSN in attendance.

[44] The construction of the second ordered batch began in January 2018, commencing with the steel-cutting ceremony of the third submarine, Illustrious, which was attended by representatives from TKMS and the DSTA.

[45][46] In April 2021, German news outlet Lübecker Nachrichten reported that a Type 218SG submarine, presumably either the Invincible or the Impeccable, had suffered fire outbreak during its sea trials.

[50] In May 2023, Impeccable, which had completed its sea trials earlier that year, was loaded onto a heavy-lift transport ship, the Rolldock Storm, for the transit trip to Singapore.

[52] Later that month, MINDEF announced that Impeccable would undergo a new set of local sea trials and workup aimed at achieving operationalization prior to its commissioning later in the year.