An amphibious assault can open new fronts and totally change the operational and strategic situation. Amphibious assault often depends on the principles of surprise and tempo.   The principles of war, surprise and tempo are the main focus in this thesis. The context consists of the operational type, amphibious assault. The main problem that the study will try to answer is the paradox that theorists highlight these principles as essential conditions for amphibious operations, but they have not developed specifically why and how. In this context it is interesting because there are a number of paradoxes between the type of operation and the principles.   To be able to examine the principles a higher degree of concreteness has to be applied. This is done by examining what other modern theorists has developed on the principles. The most prominent factors then become the thesis operationalized indicators that provides the analysis tool for the thesis. The theory will then be tested by analysing two case studies, Operation Shingle in Anzio and Operation Chromite in Inchon.   The result shows that the indicators of surprise consists of unexpected acting, diversion and operations security. The results of the case study regarding this comes to the conclusions that unexpected acting and operation security are key factors. The indicators of tempo are rapid decision-making and quick physical movement. The case study result indicates that both are criterias for success and are based on a mutual relationship between the indicators.

Defence against an amphibious assault is an extremely difficult endeavour as is evident by the long line of successful amphibious assaults undertaken throughout history. Field fortifications has to a large extent been present in defences, yet little research has been done on the effects of field fortifications in preventing successful landing operations. Therefore, this thesis examines the specific role of field fortifications in defence against amphibious assaults. The purpose is to combine theories about amphibious operations with concepts of field fortifications to add depth to existing theories as two historical examples are examined.  Results show that the existing theories’ notions, especially regarding the devastating effects of indirect fire and pre-bombardment, are not true for the two cases of study. It is furthermore shown that avoiding terrain where the enemy’s defence is focused was of little consequence for whether the assault was successful or not. Of greater importance was the power imbalance of attacker versus defender. Lastly, it is argued that the development of advanced weaponry plausibly levels out the power imbalance as effects of pre-bombardment is more likely to be successful.