The United States initiated the Manhattan Project in 1942 in collaboration with the United Kingdom.
Notes on verification
Well-corroborated by multiple independent sources including Wikipedia's main and specialized articles; minor simplification of the multi-stage UK-US collaboration timeline (Tube Alloys, Quebec Agreement) but core facts are accurate. [needs ≥1 corroborating source on a different host than https://en.wikipedia.org/wiki/History_of_nuclear_weapons; got 0 after cascade filter | tier=unverified indep_score=0.0 clusters=0 claim_tier=everyday] [harvest 2026-09-15: +4 source(s) on new hosts; tier unverified->gold indep=1.0 clusters=4] [kind-backfill 2026-09-15: kind=empirical eligibility=high]
Sources
- History of nuclear weapons (wikipedia)
- https://ahf.nuclearmuseum.org/ahf/history/british-nuclear-program/ (corroboration)
- https://cup.columbia.edu/book/the-manhattan-project/9780231131537/ (corroboration)
- https://www.lanl.gov/media/publications/the-vault/1023-los-alamos-and-the-british-mission (corroboration)
- https://home.nps.gov/mapr/learn/historyculture/timeline.htm (corroboration)