diff --git a/src/field/arena.ts b/src/field/arena.ts
index e8defbd1a8e..8d0906c649f 100644
--- a/src/field/arena.ts
+++ b/src/field/arena.ts
@@ -391,16 +391,16 @@ export class Arena {
     return true;
   }
 
-  isMoveWeatherCancelled(move: Move) {
-    return this.weather && !this.weather.isEffectSuppressed(this.scene) && this.weather.isMoveWeatherCancelled(move);
+  isMoveWeatherCancelled(move: Move): boolean {
+    return (this.weather && !this.weather.isEffectSuppressed(this.scene) && this.weather.isMoveWeatherCancelled(move)) as boolean;
   }
 
-  isMoveTerrainCancelled(user: Pokemon, targets: BattlerIndex[], move: Move) {
-    return this.terrain && this.terrain.isMoveTerrainCancelled(user, targets, move);
+  isMoveTerrainCancelled(user: Pokemon, targets: BattlerIndex[], move: Move): boolean {
+    return (this.terrain && this.terrain.isMoveTerrainCancelled(user, targets, move)) as boolean;
   }
 
-  getTerrainType() : TerrainType {
-    return this.terrain?.terrainType || TerrainType.NONE;
+  getTerrainType(): TerrainType {
+    return this.terrain?.terrainType ?? TerrainType.NONE;
   }
 
   getAttackTypeMultiplier(attackType: Type, grounded: boolean): number {
diff --git a/src/field/pokemon.ts b/src/field/pokemon.ts
index 8594d5b769b..34eb6b7a512 100644
--- a/src/field/pokemon.ts
+++ b/src/field/pokemon.ts
@@ -4368,8 +4368,8 @@ export class PokemonBattleSummonData {
 export class PokemonTurnData {
   public flinched: boolean = false;
   public acted: boolean = false;
-  public hitCount: number;
-  public hitsLeft: number;
+  public hitCount: number = 0;
+  public hitsLeft: number = 0;
   public damageDealt: number = 0;
   public currDamageDealt: number = 0;
   public damageTaken: number = 0;
diff --git a/src/phases/move-phase.ts b/src/phases/move-phase.ts
index d841825b333..cba5d18fa2e 100644
--- a/src/phases/move-phase.ts
+++ b/src/phases/move-phase.ts
@@ -1,27 +1,27 @@
-import BattleScene from "#app/battle-scene.js";
-import { BattlerIndex } from "#app/battle.js";
-import { applyAbAttrs, applyPostMoveUsedAbAttrs, applyPreAttackAbAttrs, BlockRedirectAbAttr, IncreasePpAbAttr, PokemonTypeChangeAbAttr, PostMoveUsedAbAttr, RedirectMoveAbAttr } from "#app/data/ability.js";
-import { CommonAnim } from "#app/data/battle-anims.js";
-import { BattlerTagLapseType, CenterOfAttentionTag } from "#app/data/battler-tags.js";
-import { allMoves, applyMoveAttrs, BypassRedirectAttr, BypassSleepAttr, ChargeAttr, CopyMoveAttr, HealStatusEffectAttr, MoveFlags, PreMoveMessageAttr } from "#app/data/move.js";
-import { SpeciesFormChangePreMoveTrigger } from "#app/data/pokemon-forms.js";
-import { getStatusEffectActivationText, getStatusEffectHealText } from "#app/data/status-effect.js";
-import { Type } from "#app/data/type.js";
-import { getTerrainBlockMessage } from "#app/data/weather.js";
-import { Abilities } from "#app/enums/abilities.js";
-import { BattlerTagType } from "#app/enums/battler-tag-type.js";
-import { Moves } from "#app/enums/moves.js";
-import { StatusEffect } from "#app/enums/status-effect.js";
-import { MoveUsedEvent } from "#app/events/battle-scene.js";
-import Pokemon, { MoveResult, PokemonMove, TurnMove } from "#app/field/pokemon.js";
-import { getPokemonNameWithAffix } from "#app/messages.js";
-import * as Utils from "#app/utils.js";
+import { BattlerIndex } from "#app/battle";
+import BattleScene from "#app/battle-scene";
+import { applyAbAttrs, applyPostMoveUsedAbAttrs, applyPreAttackAbAttrs, BlockRedirectAbAttr, IncreasePpAbAttr, PokemonTypeChangeAbAttr, PostMoveUsedAbAttr, RedirectMoveAbAttr } from "#app/data/ability";
+import { CommonAnim } from "#app/data/battle-anims";
+import { BattlerTagLapseType, CenterOfAttentionTag } from "#app/data/battler-tags";
+import { allMoves, applyMoveAttrs, BypassRedirectAttr, BypassSleepAttr, ChargeAttr, CopyMoveAttr, HealStatusEffectAttr, MoveFlags, PreMoveMessageAttr } from "#app/data/move";
+import { SpeciesFormChangePreMoveTrigger } from "#app/data/pokemon-forms";
+import { getStatusEffectActivationText, getStatusEffectHealText } from "#app/data/status-effect";
+import { Type } from "#app/data/type";
+import { getTerrainBlockMessage } from "#app/data/weather";
+import { Abilities } from "#app/enums/abilities";
+import { BattlerTagType } from "#app/enums/battler-tag-type";
+import { Moves } from "#app/enums/moves";
+import { StatusEffect } from "#app/enums/status-effect";
+import { MoveUsedEvent } from "#app/events/battle-scene";
+import Pokemon, { MoveResult, PokemonMove, TurnMove } from "#app/field/pokemon";
+import { getPokemonNameWithAffix } from "#app/messages";
+import { BattlePhase } from "#app/phases/battle-phase";
+import { CommonAnimPhase } from "#app/phases/common-anim-phase";
+import { MoveEffectPhase } from "#app/phases/move-effect-phase";
+import { MoveEndPhase } from "#app/phases/move-end-phase";
+import { ShowAbilityPhase } from "#app/phases/show-ability-phase";
+import * as Utils from "#app/utils";
 import i18next from "i18next";
-import { BattlePhase } from "./battle-phase";
-import { CommonAnimPhase } from "./common-anim-phase";
-import { MoveEffectPhase } from "./move-effect-phase";
-import { MoveEndPhase } from "./move-end-phase";
-import { ShowAbilityPhase } from "./show-ability-phase";
 
 export class MovePhase extends BattlePhase {
   public pokemon: Pokemon;
@@ -86,8 +86,8 @@ export class MovePhase extends BattlePhase {
 
     // Reset hit-related turn data when starting follow-up moves (e.g. Metronomed moves, Dancer repeats)
     if (this.followUp) {
-      this.pokemon.turnData.hitsLeft = undefined;
-      this.pokemon.turnData.hitCount = undefined;
+      this.pokemon.turnData.hitsLeft = 0;
+      this.pokemon.turnData.hitCount = 0;
     }
 
     /**
@@ -188,7 +188,7 @@ export class MovePhase extends BattlePhase {
 
     // TODO: Clean up implementation of two-turn moves.
     if (moveQueue.length > 0) { // Using .shift here clears out two turn moves once they've been used
-      this.ignorePp = moveQueue.shift().ignorePP;
+      this.ignorePp = moveQueue.shift()?.ignorePP ?? false;
     }
 
     // "commit" to using the move, deducting PP.
@@ -220,7 +220,7 @@ export class MovePhase extends BattlePhase {
 
     // Move conditions assume the move has a single target (is this sustainable?)
     const passesConditions = move.applyConditions(this.pokemon, targets[0], move);
-    const failureMessage = move.getFailedText(this.pokemon, targets[0], move, null);
+    const failureMessage = move.getFailedText(this.pokemon, targets[0], move, new Utils.BooleanHolder(false));
 
     const failedWithMessage = failureMessage !== null && failureMessage !== undefined;
     let failedDueToWeather: boolean, failedDueToTerrain: boolean;
@@ -233,6 +233,7 @@ export class MovePhase extends BattlePhase {
       }
     }
 
+    // @ts-expect-error
     const success = passesConditions && !failedWithMessage && !failedDueToWeather && !failedDueToTerrain;
 
     /**
@@ -258,7 +259,7 @@ export class MovePhase extends BattlePhase {
 
       if (failedWithMessage) {
         failedText = failureMessage;
-
+        // @ts-expect-error
       } else if (failedDueToTerrain) {
         failedText = getTerrainBlockMessage(this.pokemon, this.scene.arena.getTerrainType());
       }
@@ -305,7 +306,7 @@ export class MovePhase extends BattlePhase {
       const redirectTarget = new Utils.IntegerHolder(currentTarget);
 
       // check move redirection abilities of every pokemon *except* the user.
-      this.scene.getField(true).filter(p => p !== this.pokemon).forEach(p => applyAbAttrs(RedirectMoveAbAttr, p, null, this.move.moveId, redirectTarget));
+      this.scene.getField(true).filter(p => p !== this.pokemon).forEach(p => applyAbAttrs(RedirectMoveAbAttr, p, null, false, this.move.moveId, redirectTarget));
 
       // check for center-of-attention tags (note that this will override redirect abilities)
       this.pokemon.getOpponents().forEach(p => {
@@ -411,10 +412,10 @@ export class MovePhase extends BattlePhase {
       pokemonNameWithAffix: getPokemonNameWithAffix(this.pokemon),
       moveName: this.move.getName()
     }), 500);
-    applyMoveAttrs(PreMoveMessageAttr, this.pokemon, this.pokemon.getOpponents().find(() => true), this.move.getMove());
+    applyMoveAttrs(PreMoveMessageAttr, this.pokemon, this.pokemon.getOpponents().find(() => true) ?? null, this.move.getMove());
   }
 
-  showFailedText(failedText: string = null): void {
-    this.scene.queueMessage(failedText || i18next.t("battle:attackFailed"));
+  showFailedText(failedText?: string): void {
+    this.scene.queueMessage(failedText ?? i18next.t("battle:attackFailed"));
   }
 }