Operation Hardtack I & II was a series of 72 nuclear tests conducted by the United States in 1958. With test moratoriums on the horizon, American weapons labs rushed out many new designs. Hardtack I was carried out in the Pacific Ocean, at Bikini Atoll, Enewetak Atoll, and Johnston Island.
Hardtack II was carried out later that year at the Nevada Test Site. Hardtack II consisted exclusively of low-yield atmospheric and underground tests, and 17 one-point safety tests. All Hardtack I tests were barge shots, and all Hardtack II tests were undergound, unless otherwise noted:

Hardtack I Test Blasts

Test Name	Date	Location	Yield	Note
Yucca	28 April, 1958	Enewetak	1.7 kilotons	high-altitude balloon test
Cactus	5 May, 1958	Enewetak	18 kilotons	surface shot
Fir	11 May, 1958	Bikini Atoll	1.36 megatons	93.4% fusion yield
Butternut	11 May, 1958	Enewetak	81 kilotons
Koa	12 May, 1958	Enewetak	1.37 megatons
Wahoo	16 May, 1958	Enewetak	9 kilotons	deep underwater test
Holly	20 May, 1958	Enewetak	5.9 kilotons
Nutmeg	21 May, 1958	Bikini Atoll	25.1 kilotons
Yellowwood	26 May, 1958	Enewetak	330 kilotons	expected yield 2.5 Megatons
Magnolia	26 May, 1958	Enewetak	57 kilotons
Tobacco	30 May, 1958	Enewetak	11.6 kilotons	2nd stage failed to ignite
Sycamore	31 May, 1958	Bikini Atoll	9 kilotons	deep underwater test
Rose	20 May, 1958	Enewetak	5.9 kilotons
Umbrella	21 May, 1958	Bikini Atoll	25.1 kilotons
Maple	26 May, 1958	Enewetak	330 kilotons	expected yield 2.5 Megatons
Aspen	26 May, 1958	Enewetak	57 kilotons	fired in Castle Bravo crater
Walnut	14 June, 1958	Enewetak	1.45 kilotons
Linden	18 June, 1958	Enewetak	11 kilotons
Redwood	27 June, 1958	Bikini Atoll	412 kilotons
Elder	27 June, 1958	Enewetak	880 kilotons
Oak	28 June, 1958	Enewetak	8.9 megatons
Hickory	30 June, 1958	Bikini Atoll	14 kilotons
Sequoia	1 July, 1958	Enewetak	5.2 kilotons
Cedar	2 July, 1958	Bikini Atoll	220 kilotons
Dogwood	5 July, 1958	Enewetak	397 kilotons
Poplar	12 July, 1958	Bikini Atoll	9.3 megatons
Scaevola	14 July, 1958	Enewetak	zero	safety test
Pisonia	17 July, 1958	Enewetak	255 kilotons
Juniper	22 July, 1958	Bikini Atoll	65 kilotons
Olive	22 July, 1958	Enewetak	202 kilotons
Pine	26 July, 1958	Bikini Atoll	2 megatons	expected yield 4-6 megatons
Teak	1 August, 1958	Johnston Island	3.8 megatons	Redstone missile test, 252,000 foot burst height
Quince	6 August, 1958	Enewetak	zero	fizzle
Orange	12 August, 1958	Johnston Island	3.8 megatons	Redstone missile test, 141,000 foot burst height
Fig	18 August, 1958	Enewetak	0.02 kilotons	last test at Enewetak

Hardtack II Test Blasts

Test Name	Date	Location	Yield	Note
Otero	12 September, 1958	NTS Area 3q	0.038 kilotons	1PT, failed
Bernalillo	17 September, 1958	NTS Area 3h	0.015 kilotons	1PT; unsafe
Eddy	19 September, 1958	NTS Area 7b	0.083 kilotons	ballon shot
Luna	21 September, 1958	NTS Area 3m	0.0015 kilotons	1PT; unsafe
Mercury	23 September, 1958	NTS Area 12f	"slight"	1PT
Valencia	26 September, 1958	NTS Area 3r	0.002 kilotons	1PT
Mars	28 September, 1958	NTS Area 12f	0.013 kilotons	1PT
Mora	29 September, 1958	NTS Area 7b	2 kilotons	ballon shot; fizzled
Hidalgo	5 October, 1958	NTS Area 7b	0.077 kilotons	ballon test; failed
Colfax	5 October, 1958	NTS Area 3k	0.0055 kilotons	1PT; failed
Tamalpais	8 October, 1958	NTS Area 12b	0.072 kilotons
Quay	10 October, 1958	NTS Area 7c	0.079 kilotons	tower shot
Lea	13 October, 1958	NTS Area 7b	1.4 kilotons	ballon shot; fizzled
Neptune	14 October, 1958	NTS Area 12c	0.115 kilotons	1pt; failed
Hamilton	15 October, 1958	NTS Area 5	0.0012	tower shot; fizzled
Logan	16 October, 1958	NTS Area 12e	5 kilotons
Dona Ana	16 October, 1958	NTS Area 7b	0.037 kilotons
Vesta	17 October, 1958	NTS Area 9e	0.024 kilotons	1pt; surface shot; failed
Rio Arriba	18 October, 1958	NTS Area 3s	0.090 kilotons	tower shot
San Juan	20 October, 1958	NTS Area 3p	"zero"	1pt
Sorocco	22 October, 1958	NTS Area 3b	6 kilotons	balloon shot
Wrangell	22 October, 1958	NTS Area 5	0.115 kilotons	balloon shot; fizzle
Oberon	22 October, 1958	NTS Area 8a	"zero"	1pt
Rushmore	22 October, 1958	NTS Area 9a	0.188 kilotons	balloon test; fizzle
Catron	24 October, 1958	NTS Area 3T	0.021 kilotons	1pt; failed
Juno	24 October, 1958	NTS Area 9f	0.0017 kilotons	1pt, surface shot
Ceres	26 October, 1958	NTS Area 3b	0.0007 kilotons	1pt; tower shot
Sanford	26 October, 1958	NTS Area 5	4.9 kilotons	balloon shot
De Baca	26 October, 1958	NTS Area 7b	2.2 kilotons	balloon shot
Chavez	27 October, 1958	NTS Area 3u	0.0006 kilotons	1pt; tower shot; failed
Evans	29 October, 1958	NTS Area 12b	0.055 kilotons	fizzle
Mazama	29 October, 1958	NTS Area 9	"zero"	fizzle
Humbodt	29 October, 1958	NTS Area 3v	0.0078 kilotons	tower shot
Santa Fe	30 October, 1958	NTS Area 7b	1.3 kilotons	balloon shot
Ganymede	30 October, 1958	NTS Area 9g	"zero"	1pt; surface shot
Blanca	30 October, 1958	NTS Area 12e	22 kilotons	largest test on Hardtack II
Santa Fe	30 October, 1958	NTS Area 7b	1.3 kilotons	balloon shot
Titania	30 October, 1958	NTS Area 3c	0.0002 kilotons	1pt; tower shot Categories: American nuclear explosive tests | 1958