Of the many theories that have been offered to ‘explain’ K-cycles, the most plausible by far is their close correlation with clusters of radical innovations associated with changes in major primary energy sources, starting with the “age” of coal and iron, followed by the “age”of steam power, railways, steel, and town gas, followed by the age of electrification, internal combustion engines and automobiles. Schumpeter (writing in 1939) suggested that the third wave would end around 1950. He expected the A-period of a fourth K-wave to begin then, with a B-period starting in the 1970s and ending around 1990. The postwar boom and the advent of nuclear power and natural gas seemed to fit that prescription. The slowdown beginning in the 1970s also fits the pattern. US oil production peaked in 1969-70. The energy crisis of 1973-74 was followed by the deepest recession since the 1930s. Nuclear power suffered a setback in the 1980s, and the on-going de-industrialization of the US accelerated. In effect, it can be argued that the fourth K-wave occurred on schedule and ended around 1990-1992, also with a deep recession. The A-period of the fifth wave presumably began then, driven by the ‘digital revolution’ ICT and the internet. But recent events, especially since 2000, also suggest that the pattern may have broken. This paper reviews the evidence for such a view. The relevance to US National Security is spelled out clearly in Michael Klare's book “Resource Wars” (2001) which virtually predicted 9/11 and the US attack on Iraq.