Updates to ARMA 2: Operation Arrowhead have been released. The updates will be applied automatically when your Steam client is restarted.

ARMA 2: Operation Arrowhead

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VERSION 1.55 HIGHLIGHTS
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* Numerous stability and functionality fixes and improvements
* Reworked MP SP/MP Mission Selector
* Various visual optimizations and fidelity additions
* Added many new scripting commands and event-handlers
* AI behaviour related fixes and improvements

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Version 1.54-1.55 Changelog
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Engine
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* Fixed: Subordinates would ignore their leaders' GetIn/GetOut commands in some MP situations.
* Fixed: Tanks were jumping a lot when driving over stones far from a camera (http://dev-heaven.net/issues/1707).
* Optimized: Improved performance when wheeled or tracked vehicles are moving (related to ground trace maintenance).
* Fixed: Possible player desync after DeleteVehicle command when player is a gunner.
* Fixed: Audibility of the VoN direct channel and conversations are now based on the player camera position, instead of the unit position.
* Improved: Tree LOD blending is now smoother in many situations.
* New: Free camera can be locked to plain objects like trees.
* New: New MP UI for Create Game (both host and remote).
* Fixed: Fps degradation when vehicles collided with rocks (http://dev-heaven.net/issues/2490)
* New: -skipintro command line option to disable loading menu cutscenes.
* Optimized: File cache memory handling is now faster.
* Changed: foreach variable _index renamed to _forEachIndex
* Fixed: Stop firing at vehicle crew once it is dead. (http://dev-heaven.net/issues/5183)
* Fixed: Rpt file no longer created in local settings when -profile is used (http://dev-heaven.net/issues/13308)
* Fixed: Some texture or model files not loaded from mod paths starting with @. (http://dev-heaven.net/issues/14039)
* Fix: Flooding of RPT file by "Cannot find Object" and similar messages after client disconnection.
* New: Scripting command HostMission.
* FIX: Engine crash with diag_log versus %
* New: MP Diagnostics logged into the mpStatistics.log file at the end of mission.
* New: VSync config option
* New: GetResolution script function
* New: forEach: variable _index added to retrieve the position of _x within the Array
* New: getVariable: default value can be defined
* Changed: Preprocessor error no longer terminates the game.
* New: getTerrainHeightASL script function
* Fixed: Reduced z-fight in scopes.
* New: event handler "fired" returns magazine name and object of projectile.
* Fixed: Slow animation step on some buildings (doors on LHD,..)
* Fixed: Alpha blend in fog.
* New: mergeConfigFile script function
* Fixed: Heads of distant soldiers were sometimes invisible (http://dev-heaven.net/issues/4023)
* Fixed: Fired EH (http://dev-heaven.net/issues/13971)
* Fixed: Person - helicopter collision not cause heli damage, (http://dev-heaven.net/issues/12107)
* New: setSimpleTaskTarget script function
* Fixed: SetIdentity (relate to 73319)
* Fixed: Ammo created with createvehicle inflicts no "hit" damage
* Fixed: My own shots no longer causing a stress.
* New: WeaponAssembled, WeaponDisassembled events
* Fixed: Nearby units are notified of vehicles created by CreateVehicle command immediately now.
* Fixed: AI helicopters hovering too high when deploying troops on transport unload WP.
* Improved: Animation interpolation no longer shortening hands.
* Fixed: Relative formation command (advance/fallback/flank) now working as expected.
* Improved: AI mounting vehicles or catching up with formation covering a bit less to move faster.
* New: Expansions possibly registered in Windows Registry (by some future setups) are loaded and available through ModLauncher.
When used with -mod commandline the prefix '%' should be used, such as -mod=%someInstalledMod.
* New: added addWeaponCargoGlobal, addMagazineCargoGlobal, addBackpackCargoGlobal
* Improved: Improved helicopter AI formation flying and collision avoidance.
* Fixed: MPEvents were not synchronized to clients after respawn.
* Fixed: leaveVehicle no longer unassigns units from other groups (http://dev-heaven.net/issues/3476)
* Changed: Event handlers evaluation, EH are now processed after simulation.
* Fixed: AI soldier unable to fire at targets below or above itself (http://dev-heaven.net/issues/13668)
* New: addBackpackCargo script function
* New: Multiplayer Event MPRespawn synchronized on all clients but triggered only on the client where respawn happens.
* Fixed: Client had problems taking weapon from remote vehicle (supply target was handled localy)
* New: Multiplayer Event Handlers MPKilled and MPHit. Their event handlers are synchronized over network to be the same on all clients.
Moreover, when the MPKilled or MPHit event occurs it is triggered on all clients, ie. it works in global manner.
Use them by new scripting commands addMPEventHandler, removeMPEventHandler and removeAllMPEventHandlers.
* Fixed: Join group changes unit's side
* Changed: Airplanes parallax HUD disabled, can be enabled by "enableParallax" in config
* Fixed: execVM with a zero sized file has freezed the game.
* Fixed: Switching vision mode with fire mode
* Fixed: AI equipped with TI see through smokes
* Fixed: Commanding units with aiming deadzone
* Fixed: crash on server when loading ban.txt
* Fixed: crash in Ka52 while player as gunner
* Fixed: Shadows sometimes disappered, esp. when sun was behind a player.
* Improved: changed tank AI driver behaviour
* New: Better clients bad CDKey checking on server.
* Fixed: Crash with AI leaving vehicle with GetOut EH (http://dev-heaven.net/issues/11011)
* Fixed: Client with bad CD key is kicked off from server instead of being politely asked to disconnect.
* Fixed: Airplanes HUDs projected into infinity.
* Improved: Tracers visible in all directions.
* Fixed: Unable to connect to servers with equalModRequired.
* Fixed: AI stuck while in combat/stealth mode
* New: Explosive shells penetrate bushes;
* Fixed: FireAtPosition aimpoint
* Fixed: Multiplayer on LAN was crashing when GameSpy server was unavailable.


Data
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* Tweaked envelope and landing speed of L39.
* Fixed respawn weapons for some TK soldiers
* Renamed faction CZ - > ACR.
* Tweaked airplanes radars.
* Parallax airplane HUD projection.

For full information about the included changes between versions 1.50 and 1.55 please visit http://community.bistudio.com/wiki/ArmA_2:_Operation_Arrowhead:_Version_History