Question

Which factors contributed to the collapse of these civilizations or regimes?

Neo-Assyria, Kingdom of Israel, Mycenaean Greece, Middle Kingdom Egypt

destruction by invasion or military conquest
environmental catastrophe
gradual acquisition of power by new groups

Answer 1

Below I list each polity, the timing of its end, and whether the three causes you named were important — with a brief explanation and degree of certainty.

Neo‑Assyria (end c. 612–609 BCE)
- Destruction by invasion or military conquest: Yes — decisive. A Babylonian–Median coalition (plus Scythian allies) besieged and sacked Nineveh (612) and destroyed the Assyrian state-centre at Harran and elsewhere; military defeat was the proximate cause.
- Environmental catastrophe: Little direct evidence that climate/environmental collapse was the primary cause. Long-term strains (overextension, economic costs of continuous warfare, possible local famines) may have weakened the empire, but environmental catastrophe is not the main explanation.
- Gradual acquisition of power by new groups: Yes/important — the power vacuum was filled by rising powers (Neo‑Babylonian and Median states) and their elites; Assyrian imperial structures were replaced rather quickly by these new polities.

Kingdom of Israel (Northern Kingdom; fall 722 BCE)
- Destruction by invasion or military conquest: Yes — the Assyrian Empire conquered Samaria in 722/721 BCE, deported populations, and incorporated the territory into Assyrian provinces.
- Environmental catastrophe: Not a major factor in the standard account. Local economic or agricultural stresses may have existed but are not central to the collapse.
- Gradual acquisition of power by new groups: Yes/partial — Assyrian resettlement policy and provincial administration inserted new populations and officials into the area, changing its demographic and political character.

Mycenaean Greece (collapse c. 1200–1100 BCE; “Late Bronze Age collapse”)
- Destruction by invasion or military conquest: Yes/partial — there is archaeological evidence for widespread destructions at many palace sites, and contemporary texts and later traditions mention “Sea Peoples” and migrations. Invasions/raids likely contributed regionally.
- Environmental catastrophe: Yes/possible/significant — palaeoclimate records and other data suggest episodes of drought, crop failure, and possibly earthquakes that disrupted agriculture and trade; these stresses likely amplified social problems.
- Gradual acquisition of power by new groups: Yes/partial — the shift from palace-centered, bureaucratic Mycenaean society to dispersed, village-based Iron Age communities could reflect population movements (e.g., Dorian migrations, though this is debated) and the rise of new local elites over generations rather than instant replacement everywhere.

Middle Kingdom Egypt (decline c. late 12th–17th centuries BCE; transition to Second Intermediate Period, Hyksos period)
- Destruction by invasion or military conquest: Yes/partial — the Hyksos (Asiatic groups) gained control in the Nile Delta and established the 15th Dynasty (c. 1650 BCE), so foreign takeover was important in the Delta and in ending centralized Middle Kingdom power, though much of Egypt’s south remained Egyptian.
- Environmental catastrophe: Yes/possible — evidence for low Nile floods, economic trouble, and famines in the later Middle Kingdom and First Intermediate Period suggests environmental stress undermined central authority.
- Gradual acquisition of power by new groups: Yes — weakening of central power allowed provincial officials (nomarchs) and local elites to assert autonomy; Hyksos emergence in the Delta was a mix of migration, infiltration, and then political takeover rather than only a single catastrophic conquest.

Summary
- Neo‑Assyria and the Kingdom of Israel fell chiefly through military conquest (Assyrian defeat and Assyrian conquest respectively), with new powers replacing them.
- Mycenaean Greece’s collapse was multi-causal: invasions/raids, environmental stress (drought, seismicity), internal collapse of palace systems, and later population/migration shifts all likely played roles.
- Middle Kingdom Egypt weakened through a combination of environmental stress and internal decentralization, which opened the way for Asiatic groups (Hyksos) and local elites to acquire power.

If you want, I can give primary sources or archaeological indicators for any of these points (e.g., Assyrian/Babylonian chronicles, destruction layers at Mycenaean palaces, Nile flood records).