Operation Grapple


Operation Grapple, also known as the Grapple series, represents a significant chapter in the United Kingdom’s pursuit of nuclear capabilities during the mid-20th century. It was a series of tests aimed at developing a functional thermonuclear bomb, more commonly referred to as an H-bomb or hydrogen bomb.

Before Operation Grapple, the UK had conducted nuclear bomb tests in Australia. However, concerns about contamination arising from these tests, coupled with the anticipation of increased fallout from H-bombs, prompted a decision to relocate the testing program to a more remote location in the Pacific Ocean.

Two strategically chosen islands were selected for this endeavour: Christmas Island, serving as the operational base for the test force, and Malden Island, located approximately 360 miles to the south, designated as the primary test site.

Commencement of Work

The preparations for Operation Grapple began in 1956 with the construction of a base on Christmas Island. This base included the creation of a new 7,000-foot runway, the development of an additional 25 miles of roads, and the construction of various buildings and housing facilities (mainly tents) to accommodate the approximately 1200 personnel. This infrastructure was established on the northern end of Christmas Island, setting the stage for the upcoming nuclear tests.

Number of tests and locations

To minimize the risk of fallout, all nine tests conducted as part of Operation Grapple were designed as air bursts. In the first round of tests, the devices were deployed from Vickers Valiant bombers. However, for the second round, a cost-saving and time-efficient approach was adopted, conducting the tests offshore of Christmas Island.

In total, Operation Grapple encompassed nine nuclear tests, contributing to the development of the UK’s thermonuclear capabilities.

Task Force 308 (Operation Grapple)

To coordinate and execute Operation Grapple effectively, a tri-service task force known as “Task Force 308” was formed. In the spring of 1957, the RAF element of this task force, designated No. 160 Wing, was established at RAF Hornchurch.

This Task Force was composed from the following units:

  • No. 206 and No. 240 Squadrons RAF provided Avro Shackleton Mk2s for maritime search and reconnaissance, ensuring the safety and security of the test operation.
  • No. 49 Squadron RAF contributed Vickers Valiant bombers, which were instrumental in deploying the nuclear devices during the tests.
  • No. 76 Squadron RAF played a critical role in radiation sampling, utilizing six EE Canberra B.6 aircraft to gather essential data.
  • No. 100 Squadron furnished four EE Canberra PR.7 aircraft for long-range weather reconnaissance, aiding in the planning and execution of the tests.
  • No. 58 Squadron provided two EE Canberra PR.7 aircraft tasked with transporting radioactive samples back to the UK for further analysis.

Operation Grapple 1

Test 1

15 May 1957, codename ‘Short Granite’, Valiant XD818 dropped a 1 megaton device which exploded 8,000 feet above Malden Island. Only a 300 kiloton yield was achieved from the device.

Test 2

31 May 1957 codename ‘Orange Herald’, this was actually a fission bomb, which detonated with a 720 kiloton yield.

Test 3

19 June 1957, codename ‘Purple Granite’, another poor yield of 200 kilotons.

The Grapple 1 tests were a disappointment to the British government as the yields were much lower than expected. However, much had been learned and changes made for the next round of testing.

It was decided to do another set of testing as part of Grapple X, Grapple Y and Grapple Z.

Operation Grapple X

8 November 1957, Valiant XD824 dropped a device offshore of Christmas Island, the yield was much bigger than expected at 1.8 megatons. The blast caused some structural damage to the base on the north of the island, 24 miles away.

Operation Grapple Y

28 April 1958, Valiant XD825 dropped the UKs first true Hydrogen bomb, the yield was 2 megatons.

operation Grapple Z

Grapple Z was a series of 4 tests of lower yields, 2 tests were air dropped and 2 were balloon deployed.

Test 1

22 August 1958, codename ‘Pendant’, the device was suspended under 4 barrage balloons, a yield of 24 kilotons was recorded.

Test 2

2 September 1958, codename ‘Flagpole’, dropped by Valiant XD822, a yield of 1.2 megatons was achieved.

Test 3

11 September 1958, codename ‘Halliard 1’, dropped by Valiant XD827, a yield of 800 kilotons was achieved.

Test 4

23 September 1958, codename ‘Burgee’, the device was suspended under barrage balloons and yielded 25 kilotons. This was the UKs last ever atmospheric nuclear test.

After the tests

Following the conclusion of the Operation Grapple tests, it’s noteworthy that the UK did not proceed to develop hydrogen bombs (H-bombs) based on the Grapple designs. However, the testing phase did yield valuable insights and technological advancements that influenced subsequent developments in the UK’s nuclear arsenal.

One notable outcome of these tests was the genesis of the “Green Grass” atomic fission bomb, derived from the knowledge and experience gained during Operation Grapple, particularly from the ‘Orange Herald’ fission device. This adaptation and refinement of nuclear technology underscored the enduring impact of the Grapple program on the UK’s nuclear capabilities.

Moreover, Operation Grapple had broader geopolitical implications. The tests prompted the United States to recognize the value of sharing nuclear weapon technology with the UK. This mutual collaboration proved beneficial for both nations. The UK, for instance, possessed expertise in areas like electronics and circuitry related to thermonuclear weapons that exceeded the American capabilities. This realization led to a more cooperative exchange of knowledge and technology, ultimately strengthening the nuclear capabilities of both the UK and the USA. The synergy between the two nations in the field of nuclear weaponry marked a pivotal shift in their strategic partnership during the Cold War era.

The Aircraft (images not to scale)

Illustration of Vickers Valiant XD818 from Operation Grapple
Illustration of Vickers Valiant XD818

Royal Air Force Vickers Valiant, No 49 Squadron.



Christmas Island, now called Kiritimati

Malden Island

Further reading


A great looking t-shirt based on my Vickers Valiant illustration on various products on Redbubble.

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