Editing Tegetthoff-class battleship (section)

=== Armor ===
The ''Tegetthoff''-class ships were protected at the waterline with an [[Belt armor|armor belt]] which measured {{convert|280|mm|0|sp=us}} thick in the central citadel, where the most important parts of the ship were located. This armor belt was located between the midpoints of the fore and aft [[barbette]]s, and thinned to {{convert|150|mm|in|sp=us}} further towards the bow and stern, but did not reach either. It was continued to the bow by a small patch of {{convert|110|-|130|mm|0|adj=on|sp=us}} armor. The upper armor belt had a maximum thickness of {{convert|180|mm|in|sp=us}}, but it thinned to {{convert|110|mm|in|sp=us}} from the forward barbette all the way to the bow. The casemate armor was also {{convert|180|mm|in|sp=us}} thick.{{sfn|Sieche|1991|pp=132–133}}

The sides of the main gun turrets, barbettes, and main conning tower were protected by {{convert|280|mm|0|sp=us}} of armor, except for the turret and conning tower roofs which were {{convert|60|to|150|mm|0|sp=us}} thick. The thickness of the decks ranged from {{convert|30|to|48|mm|0|sp=us}} in two layers. The underwater protection system consisted of the extension of the double-bottom upwards to the lower edge of the waterline armor belt, with a thin {{convert|10|mm|1|adj=on|sp=us}} plate acting as the outermost bulkhead. It was backed by a [[torpedo bulkhead]] that consisted of two {{convert|25|mm|0|adj=on|sp=us}} plates.{{sfn|Sieche|1991|pp=132–133}} The total thickness of this system was only {{convert|1.60|m|ftin|0|sp=us}}, which made it incapable of containing a torpedo warhead detonation or mine explosion without rupturing.{{sfn|Sieche|1991|p=135}}

In the spring of 1909, Montecuccoli sent an officer from the Naval Section of the War Ministry to Berlin in order to obtain input from [[Alfred von Tirpitz]] on the design of the ''Tegetthoff'' class. The Imperial German Navy had conducted gunnery and torpedo tests and concluded that, "The angle between [the] armored deck and belt armor should be as flat as possible", and that "The armored torpedo bulkhead should be angled inwards, the second longitudinal bulkhead outwards. The distance of the torpedo bulkhead from the outer plating should be raised from 2.5 to 4 meters."{{sfn|Sieche|1991|p=118}} While Popper adopted several of Tirpitz's suggestions regarding the external layout of the belt armor for the ''Tegetthoff'' class, the internal modifications put forward by the Imperial German Navy were not implemented.{{sfn|Sieche|1991|p=119}}