India's submarine decade: P75I IGA signed with Germany, third SSBN commissioned, AIP refit ready

Summary

India's submarine fleet is expanding simultaneously across conventional and nuclear tracks. On the conventional side: INS Vagsheer, the sixth and final Scorpene-class submarine under the P75 programme, was commissioned at Naval Dockyard Mumbai on 15 January 2025, closing a 17-year build cycle with Mazagon Dock Shipbuilders and Naval Group of France. The successor programme, P75I, moved to a new bilateral axis: Spain's Navantia was disqualified in early 2025 and Germany's TKMS emerged as sole qualifying bidder for six Type-214 AIP submarines; an Inter-Governmental Agreement was signed on 12-13 January 2026 during German Chancellor Friedrich Merz's state visit to New Delhi, and the Finance Ministry cleared the deal on 28 May 2026. Cabinet Committee on Security approval is the remaining gate before the contract, valued between Rs 70,000 and Rs 99,000 crore, can be signed. Separately, DRDO's indigenous Air Independent Propulsion module, based on phosphoric acid fuel cells, completed qualification and is ready for installation aboard INS Khanderi during a July 2026 refit, the first time Indian-designed AIP will be fitted to a front-line submarine. On the nuclear side: India's third ballistic missile submarine, INS Aridhaman (S4), was reported commissioned in April 2026 by Indian defence publications; the government has not officially confirmed the date, consistent with India's practice on nuclear programmes. INS Aridhaman carries eight VLS tubes capable of launching K-4 (3,500 km range) or K-15 SLBMs. The INS Varsha nuclear submarine base at Rambilli in Andhra Pradesh, designed to shelter SSBNs in hardened berths, is targeted for initial operational capability in 2026.

The split

Indian coverage (The Hindu, Business Standard, The Print) frames the P75I IGA as strategic diversification: Germany replaces Spain and adds a non-traditional partner to India's submarine supply chain, reducing concentration in French and Russian technology. European defence-industrial press (Army Recognition, Naval News) reads the IGA as TKMS's most significant export submarine contract and a marker of Germany's post-Ukraine willingness to become a serious defence exporter. Pakistani commentary (Jang, Dawn) contextualises the SSBN programme as the structural factor behind any India-Pakistan nuclear calculus, noting that INS Aridhaman's commissioning means India now maintains a continuous at-sea nuclear deterrent. Chinese state-aligned outlets (Global Times) have previously described Indian SSBNs as "destabilising the Bay of Bengal," though Beijing's official position does not comment on the P75I.

By the numbers

• Rs 70,000-99,000 crore ($8.4-11.9B), P75I deal value for six Type-214 AIP submarines.
• January 12-13 2026, P75I IGA signed during German Chancellor Merz's New Delhi visit.
• May 28 2026, Finance Ministry clearance of P75I IGA.
• January 15 2025, INS Vagsheer commissioned, completing the six-boat Scorpene/Kalvari programme.
• 8, VLS tubes on INS Aridhaman, capable of K-4 SLBMs with 3,500 km range.
• 3, total SSBNs in Indian service once INS Aridhaman is confirmed operational.

Why it matters

P75I closes the most glaring gap in India's conventional submarine force: the entire Scorpene fleet lacks AIP, meaning boats must surface or snorkel frequently and are detectible at a range that disadvantages them in the Andaman Sea and Arabian Sea operational areas. Six Type-214s with German AIP would give India a continuous conventional-submarine capability comparable to what Pakistan operates with its Agosta-90B fleet. The indigenous DRDO AIP programme, if it works aboard INS Khanderi, could also retrofit older boats at far lower cost than new-builds. On the nuclear track, three SSBNs means India can maintain one on deterrent patrol, one in maintenance, and one in training, roughly the minimum for a credible continuous at-sea deterrent. The INS Varsha base matters because it removes a single chokepoint vulnerability: dispersed hardened berths complicate any adversary's first-strike planning.

What to watch

• CCS approval of the P75I commercial contract and formal signing date.
• DRDO AIP retrofit performance aboard INS Khanderi and whether the module is cleared for the broader fleet.
• INS Varsha base operational milestone.
• Whether the three-boat Scorpene follow-on (under informal discussion at Rs 36,000 crore) is formally sanctioned.
• Official confirmation of INS Aridhaman's commissioning and patrol schedule.