Strategy Pattern - C++

I'm having an issue implementing a strategy pattern to my project. I created all the files necessary, however I am getting an error with my new call in main as I can't seem to initialize a strategy to what I want.

Strategy.h

/*All the classes that implement a concrete strategy should use this
The AI class will use this file as a concrete strategy
*/
using namespace std;
class Strategy{
public:
    //Method who's implementation varies depending on the strategy adopted
    //Method is therefore virtual
    virtual int execute() = 0;
 };

My three strategies Aggressive.h

#pragma once
#include <iostream>
#include "Strategy.h"

class Aggressive{
   public:
      int execute();

 };

Aggressive.cpp

#pragma once
#include <iostream>
#include "Strategy.h"
using namespace std;

class Aggressive : public Strategy{
  public:
      Aggressive(){}

      int execute(){
        cout << "The defensive player chooses to adopt an aggressive play-                             style" << endl;
        return 0;
    }

};

Defensive.h

#pragma once
#include <iostream>
#include "Strategy.h"

class Defensive{
  public:
     int execute();

};

Defensive.cpp

#include <iostream>
#include "Strategy.h"
using namespace std;

 class Defensive : public Strategy{
    public:
       int execute(){
        cout << "The defensive player chooses to adopt a defensive play-style" << endl;
    }
 };

AI.h

#pragma once
#include "Strategy.h"

class AI{
  public:
    AI();
    AI(Strategy *initStrategy);
    void setStrategy(Strategy *newStrategy);
    int executeStrategy();

};

AI.cpp

#pragma once
#include "Strategy.h"
#include "AI.h"
#include "Aggressive.h"
#include "Defensive.h"


using namespace std;

 class AI{
   private:
       Strategy *strategy;
   public:
      AI(){}
         //Plugs in specific strategy to be adopted
      AI(Strategy *initStrategy){
          this->strategy = initStrategy;
      }
      void setStrategy(Strategy *newStrategy){
          this->strategy = newStrategy;
      }
      //Method that executes a different strategy depending on what 
      //strategt was plugged in upon instantiation.
       int executeStrategy(){
          return this->strategy->execute();
      }
  };

And my temporary driver, which has an issue with new StrategyDriver.cpp

#pragma once
#include "AI.h"
#include "Strategy.h"
#include "Aggressive.h"
#include "Defensive.h"
#include "Random.h"
using namespace std;

int main(){
   AI *ai(new Aggressive());
    ai->executeStrategy();  
}

If anyone sees the issue with my code, any help would be greatly appreciated. I'm not entirely sure on how to initialize the new ai to specific strategies that were implemented.