The vast bulk of the Ministry of Defence building was designed by Vincent Harris, originally for those ill-matched arms of government, the Department of Trade and the Air Ministry. It was built in phases from 1939 to 1959. The warriors moved in in the 1960s when the Ministry of Defence was created.
The main entrance is flanked by a pair of reclining giantesses symbolising Earth and Water, by Sir Charles Wheeler (1949). The figures weigh 40 tons each and don't look an ounce less. Despite their size, they have lovely pensive expressions.
A complementary pair, Fire and Air, were planned for the south entrance but the Treasury balked at the cost.
I don't think they are much of a loss - Earth and Water are differentiated only by sitting in waves or on the ground, so presumably the others would have had a bit of cloud and a few flames but otherwise more of the same.