View source for 135 mm/45 O.T.O. Mod. 1937 (135 mm)

[[File:135 mm 45 O.T.O. Mod. 1937.jpg|thumb|x250px|Stern port battery of '''135 mm/45 O.T.O. Mod. 1937''' on [[RN Etna]]]]
== Description ==
<!-- ''Write an introduction to the article in 2-3 small paragraphs. Briefly tell us about the history of the development and combat using the weaponry and also about its features. Compile a list of air, ground, or naval vehicles that feature this weapon system in the game.'' -->
'''135 mm/45 O.T.O. Mod. 1937''' was an Italian naval gun designed as a response to the French 138.6 mm/50 and was planned to be used on a wide variety of warships - from destroyers to battleships. Most of these planes were cancelled before completion, as the gun was introduced on the verge of WW2, and didn't see any major naval engagements before the armistice.

In the game, it's best used against destroyers and coastal vessels, as it features few characteristics that make it excellent in that role. Against cruisers, it will, however, suffer significantly from having a relatively low explosive filler.

=== Vehicles equipped with this weapon ===
<!-- ''List out vehicles that are equipped with the weapon.'' -->

* {{Specs-Link|it_cruiser_capitani_romani_class_attilio_regolo}}
* {{Specs-Link|it_destroyer_comandanti_medaglie_doro}}
* {{Specs-Link|it_battleship_conte_di_cavour}}
* {{Specs-Link|it_battleship_caio_duilio}}
* {{Specs-Link|it_cruiser_etna_class}}

== General info ==
<!-- ''Tell us about the tactical and technical characteristics of the cannon or machine gun.'' -->
The gun is available in 4 different mounts. A single mount used on destroyers has the most rudimentary anti-fragmentation mount. Twin cruiser mount has insufficient protection to stop anything but the machine guns. Battleship secondaries come in two distinct mounts, and while both have a nearly identical armor, the twin-mount used on Cavour is somewhat more difficult to penetrate due to having a much smaller face and a side armor at a very steep angle.

{| class="wikitable sortable" style="text-align:center" width="100%"
! rowspan="2" data-sort-type="text" | Ship
! rowspan="2" | Guns per<br>mount
! colspan="2" | Front
! colspan="2" | Sides
! colspan="2" | Top
! colspan="2" | Elevator
|-
! Thickness<br>(mm) !! Type !! (mm) !! Type !! (mm) !! Type !! (mm) !! Type
|-
| [[RN Conte di Cavour]]|| 2 || 120 || {{Annotation|RCA|Rolled cemented armour}} || 80 || RCA || 60 || {{Annotation|RHA|Rolled homogeneous armour}} || 100 || RCA
|-
| [[RN Duilio]] || 3 || 120 || {{Annotation|RCA|Rolled cemented armour}} || 80 || RCA || 60 || {{Annotation|RHA|Rolled homogeneous armour}} || 100 || RCA
|-
| [[RN Etna]]<br/>[[RN Attilio Regolo]] || 2 ||  20 || {{Annotation|RHA|Rolled homogeneous armour}} || 6 || RHA || 6 || RHA || 0 || —
|-
| [[RN Comandante Margottini]] || 1 ||  12 || {{Annotation|AfA|Antifragmentation armour}} || 12 || AfA || 12 || AfA || 0 || —
|-
|}

=== Available ammunition ===
<!-- ''Describe the shells that are available for the weapon and their features and purpose. If it concerns autocannons or machine guns, write about different ammo belts and what is inside (which types of shells).'' -->
[[File:135 mm 45 O.T.O. Mod. 1937 - APHEBC.jpg|thumb|135 mm APHEBC Perforante shells pictured in-flight, with the aft battery of [[RN Etna]] firing in the background. Note the white tracer characteristic for armour-piercing shells.]]
The choice of shells is typical for the Italian pre-WW2 guns, limited to HE and AP against surface targets and HE-TF against aircraft. It's adequate for nearly every situation a warship can encounter.
* 135 mm HE Dirompente - Universal high-explosive round, great against frigates and torpedo boats alike, to a degree also useful against enemy destroyers, or to ignite heavier warships on fire.
* 135 mm APHEBC Perforante - The shell of choice against enemy cruisers, or to reach the [[ammo racks]] on destroyers. It lacks penetration to deal with some of the heavy cruisers or all of the battleships/battlecruisers, so against them the HE rounds would be a better choice.
* 135 mm HE-TF Contro-aerea - Time-fused high explosive shell, able to counter enemy aircraft through shrapnel. Use [[Crew skills#Gunners|Distance fuse set accuracy]] crew skill to increase the probability of fusing in the perfect spot for the kill - however, even with the skill maxed-out, shells still can explode ± 100 m away from a target at 5000 meters range, which is more than enough for the aircraft to avoid taking any damage. Still - it's by far the best round to use against enemy airplanes.

{{:{{PAGENAME}}/Ammunition|135 mm HE Dirompente, 135 mm APHEBC Perforante, 135 mm HE-TF Contro-aerea}}

=== Comparison with analogues ===
<!-- ''Give a comparative description of cannons/machine guns that have firepower equal to this weapon.'' -->
135 mm is a fairly unusual calibre, thus the comparison will be made with the guns of relatively similar calibre used as either primary guns on cruisers, or secondary guns on battleships/battlecruisers. Pure destroyer guns are intentionally skipped.

====HE====
{| class="wikitable sortable" style="text-align:center" width="100%"
|-
! colspan="2" rowspan="2" |Cannon
! rowspan="2" |Sample Ship
! rowspan="2" |Ammo
! rowspan="2" |Calibre<br>(mm)
! rowspan="2" |Muzzle Velocity<br>(m/s)
! rowspan="2" |Sustained rate of fire<br>(rounds/min)
! colspan="2" |Targeting speed<br>(°/s)
! rowspan="2" |TNT Equivalent<br>(kg)
! colspan="3" |Penetration<br>@ 0° Angle of Attack (mm)
|-
!Horizontal!!Vertical!!1,000 m!!5,000 m!!10,000 m
|-
|[[File:Italy flag.png|link=|25x25px]]
| 135 mm/45 O.T.O. Mod. 1937
| [[RN Etna]] || HE || 135 || 825 || 7.5 || 9.5 || 9.5 || 1.8 || 23 || 23 || 23
|-
|[[File:USA flag.png|link=|25x25px]]
| [[5 inch/38 Mk.12 (127 mm)]]
| [[USS Atlanta]] || HE || 127 || 792 || 15 || 21 || 13 || 3.22 || 36 || 36 || 36
|-
|[[File:Germany flag.png|link=|25x25px]]
| [[150 mm/45 SK L/45 (150 mm)]]
| [[SMS Elbing]] || HE || 150 || 835 || 7 || 4.2 || 4.2 || 1.6 || 21 || 21 || 21
|-
|[[File:USSR flag.png|link=|25x25px]]
| [[130 mm/55 pattern 1913 (130 mm)]]
| [[Imperatritsa Mariya]] || HE || 130 || 823 || 8 || 3.4 || 3.4 || 3.9 || 37 || 37 || 37
|-
|[[File:Japan flag.png|link=|25x25px]]
| [[140 mm/50 3rd Year Type (140 mm)]]
| [[IJN Sendai]] || HE || 140 || 840 || 6.2 || 8.0 || 8.0 || 3.15 || 35 || 35 || 35
|-
|[[File:France flag.png|link=|25x25px]]
| [[138.6 mm/55 model 1910 (138.6 mm)]]
| [[Lorraine]] || HE || 139 || 840 || 6 || 4.2 || 4.2 || 4.41 || 36 || 36 || 36
|-
|}

====AP/SAP====
{| class="wikitable sortable" style="text-align:center" width="100%"
|-
! colspan="2" rowspan="2" |Cannon
! rowspan="2" |Sample Ship
! rowspan="2" |Ammo
! rowspan="2" |Calibre<br>(mm)
! rowspan="2" |Muzzle Velocity<br>(m/s)
! rowspan="2" |Sustained rate of fire<br>(rounds/min)
! colspan="2" |Targeting speed<br>(°/s)
! rowspan="2" |TNT Equivalent<br>(kg)
! colspan="3" |Penetration<br>@ 0° Angle of Attack (mm)
|-
!Horizontal!!Vertical!!1,000 m!!5,000 m!!10,000 m
|-
|[[File:Italy flag.png|link=|25x25px]]
| 135 mm/45 O.T.O. Mod. 1937
| [[RN Etna]] || APHEBC || 135 || 825 || 7.5 || 9.5 || 9.5 || 1.47 || 171 || 100 || 56
|-
|[[File:USA flag.png|link=|25x25px]]
| [[5 inch/38 Mk.12 (127 mm)]]
| [[USS Atlanta]] || SP Common Mk.46 || 127 || 792 || 15 || 21 || 13 || 0.9065 || 150 || 95 || 56
|-
|[[File:Germany flag.png|link=|25x25px]]
| [[150 mm/45 SK L/45 (150 mm)]]
| [[SMS Elbing]] || APCBC || 150 || 835 || 7 || 4.2 || 4.2 || 0.99 || 238 || 153 || 93
|-
|[[File:USSR flag.png|link=|25x25px]]
| [[130 mm/55 pattern 1913 (130 mm)]]
| [[Imperatritsa Mariya]] || SAPBC || 130 || 823 || 8 || 3.4 || 3.4 || 1.67 || 178 || 115 || 71
|-
|[[File:Japan flag.png|link=|25x25px]]
| [[140 mm/50 3rd Year Type (140 mm)]]
| [[IJN Sendai]] || mod 1 SAP || 140 || 855 || 6.2 || 8.0 || 8.0 || 2.21 || 115 || 81 || 54
|-
|[[File:France flag.png|link=|25x25px]]
| [[138.6 mm/55 model 1910 (138.6 mm)]]
| [[Lorraine]] || SAPBC || 139 || 790 || 6 || 4.2 || 4.2 || 2.93 || 73 || 47 || 34
|-
|}

== Usage in battles ==
<!-- ''Describe the cannon/machine gun in the game - its distinctive features, tactics of usage against notable opponents. Please don't write a "guide" - do not impose a single point of view, but give the reader food for thought.'' -->
The biggest weakness of this gun largely determines its use. The low explosive filler makes it less effective to deal with cruisers than it might appear after reading the penetration table. Thus, it's particularly good at dealing with enemy destroyers and coastal vessels, while struggling to score kills on heavier warships.

=== Pros and cons ===
<!-- ''Summarise and briefly evaluate the weaponry in terms of its characteristics and combat effectiveness. Mark pros and cons as a list.'' -->

'''Pros:'''
* Good rate of fire
* High muzzle velocity
* Sufficient penetration to counter any light cruiser and even some of the heavy cruisers

'''Cons:'''
* Very small explosive filler of the HE and HE-TF shells

== History ==
<!-- ''Examine the history of the creation and combat usage of the weapon in more detail than in the introduction. If the historical reference turns out to be too long, take it to a separate article, taking a link to the article about the weapon and adding a block "/History" (example: <nowiki>https://wiki.warthunder.com/(Weapon-name)/History</nowiki>) and add a link to it here using the <code>main</code> template. Be sure to reference text and sources by using <code><nowiki><ref></ref></nowiki></code>, as well as adding them at the end of the article with <code><nowiki><references /></nowiki></code>.'' -->
Originally designed in response to the French [[138.6 mm/50 model 1929 (138.6 mm)|138.6 mm/50]], the 135/45 was initially planned to be introduced first with the [[RN Attilio Regolo|Capitani Romani class]] in order to counter French large destroyers (contre-torpilleur), but after the outstanding performance of the guns they got recommended for the 1937 refits of the [[Duilio (Family)|Duilio-class]]. They proved to have a lower dispersion than even the latest of the 120 mm guns, while having a higher maximum range and larger explosive filler.

During the war, a new single-mounts were developed for the Comandanti M. d'Oro-class. Only one hull of the class - [[RN Comandante Margottini]] - was launched, unarmed, to make space in the shipyard. The guns were instead planned to be used on the [[wikipedia:Yugoslav destroyer Dubrovnik|Yugoslav destroyer Dubrovnik]], but the plan didn't come to fruition before the [[wikipedia:Armistice of Cassibile|armistice]] in September 1943. Similar fate met the guns planned for [[wikipedia:Italian aircraft carrier Aquila|aircraft carrier Aquila]] and cruisers [[RN Etna|Etna]] and Vesuvio. Finally, before the armistice, the refit of the [[RN Conte di Cavour|Conte di Cavour]] was already in progress, with some of the [[120 mm/50 Armstrong model 1909 (120 mm)|120 mm guns]] being already replaced by the twin 135 mm turrets.

The single-mount guns were also used for coastal defence since early 1943, primarily on the north coast of Sardinia.

During the Cold War, a new, fully automated anti-air mount was designed for the refit of the [[wikipedia:Italian cruiser Giuseppe Garibaldi (1936)|Giuseppe Garibaldi]], but never seen any other use outside the one-off cruiser.

== Media ==
''Excellent additions to the article would be video guides, screenshots from the game, and photos.''

== See also ==
''Links to the articles on the War Thunder Wiki that you think will be useful for the reader, for example:''
* ''reference to the article about the variant of the cannon/machine gun;''
* ''references to approximate analogues by other nations and research trees.''

== External links ==
<!-- ''Paste links to sources and external resources, such as:''
* ''topic on the official game forum;''
* ''other literature.'' -->
* [[wikipedia:135 mm/45 Italian naval gun|[Wikipedia] 135 mm/45 Italian naval gun]]
* [http://www.navweaps.com/Weapons/WNIT_53-45_m1938.php <nowiki>[NavWeaps]</nowiki> 135 mm/45 (5.3") Models 1937 and 1938]
* The Weapons of the Italian Ships (Le armi delle Navi Italiane) by Erminio Bagnasco, page 35 - 37
* [https://web.archive.org/web/20210612143050/http://ejournal6.com/journals_n/1404051978.pdf From Glasgow to Genoa under three flags – the Yugoslav flotilla leader Dubrovnik] by Zvonimir Freivogel, page 87

{{Italy naval cannons}}

[[Category:Naval cannons]]