Dear General Kelly,

It has only been a few weeks since you were appointed chief of staff to President Donald J. Trump. Many others wouldn’t want the job, but someone must do it, and I can’t think of anyone more qualified than you. There can be no better preparation for it than having been a military officer.

I was a junior officer in Canada’s much smaller army before becoming the chief of staff to a much lesser political leader. But I see some similarities. My boss was also a very unconventional politician. He was a “black horse” candidate scoffed at by the political elite until he won. He was beloved by many, and loathed by many more. He routinely got into trouble for speaking his mind — was eccentric and unpredictable. The establishment and the mainstream media warred openly against him. He became a regular punchline on late night talk shows. He was the world’s most notorious mayor.

My boss was Rob Ford.

Some of the things I learned working for Ford may be useful to you. Here, for what it’s worth, are 13 entirely unsolicited observations:

1. Don’t try to change Donald Trump. He doesn’t fit the mold and that’s what his supporters love about him. Build a presidency around him that plays to his strengths. Many elected officials, appointees, and senior advisers will think they know better than your boss, and they will try to shape his presidency as they think it should be. Don’t let them.

2. Never doubt his mandate. The people elected Trump president. No one else. They want and deserve his presidency, and they knew who Trump was and what he promised to do when they voted for him. The Electoral College made him president under the rules all agreed to before the election. His mandate is legitimate and his presidency valid.

3. Focus on the objective. Your job is to select and maintain the aim. Establish clear objectives for your staff and keep them focused on the mission. Help your boss do the same for his administration. When you encounter obstacles, “picket and bypass” as if you were a Marine commander on the march. Your job isn’t to win every battle, it’s to achieve the objective.

4. Create a two-year game plan. It’s impossible to achieve everything your boss wants to do at once. Lay out a two-year campaign plan to achieve as many mandate objectives as you can. Beyond that, you’ll lose much of your ability to marshal a government in reelection mode. Be bold early. Focus on what can get done, not what should get done. But keep stretching the boundaries of the possible.

5. Break the siege. Your staff, I am sure, feel besieged. Your boss too. Mine did. In their minds, the world outside the gates hates them, misunderstands them, and is actively conspiring to destroy them. In retrospect, much of our siege mentality may have been self-induced. It doesn’t have to be. Look for opportunities to reinforce “normal” stakeholder relationships. Reach out and build coalitions where you can. That’s how you get things done in politics.

6. Protect your staff. You will be amazed, as I was, at the resilience of junior political staff. They’re much like soldiers: young, incredibly (often blindly) loyal and self-sacrificing, and willing to work until they drop for a cause they believe in. Help them see that cause. But a big part of your job will be protecting these young women and men from themselves. Don’t let them do anything that will destroy them and their careers. You may also have to protect them from your boss. He may not know how to lead and care for them. In this, you must be more than a military chief of staff; you must be their leader.

7. Etiquette matters. There is a rich and storied art to politics. Your boss is a disrupter, but you’ll have to work within the establishment to change the establishment. Recognizing and respecting their traditions matters. Find a trusted adviser who can guide you.

8. Trust your instincts. You’ve worked under pressure without respite in unforgiving environments before. As a military man, you recognize the chief of staff role as one that anticipates, facilitates, and executes, without interfering with the chain of command or usurping the authority of those in it. Your position as a trusted adviser and invisible hand who helps the president channel his authority will be well-informed by the principles you developed in uniform. They won’t fail you.

9. Give Trump answers, not options. There are two schools of thought on how political staff should support their leader. One approach is present them with multiple options from which to choose. But a better approach is for staff to consider all the options, then present a unified front to the boss. With Rob Ford, we recommended the best course of action and explained why it was better than the alternatives. He was usually (and rightly) focused on the result, not the means, so this worked well.

10. Trust somebody. No one in politics is completely trustworthy. Regardless, you must pick someone to trust. It’s essential to your sanity. You need a sounding board inside the administration. They may ultimately betray you, but you won’t succeed without them.

11. Plan your exit. Decide soon if you’ll be part of the president’s reelection team. You can help run the White House while maintaining your professional integrity. That’s harder to do on the campaign trail. You may want to remain the “steady hand” in the White House, while political operatives run the campaign. Knowing this now will affect how you align your responsibilities.

12. Keep your resume up to date. Yours is the toughest job in the White House. You’re the guy who must say “no” to the most powerful man in the world. We’ll never know when you do this, because you’ll do it in private. You’ll make your case in confidence and he’ll decide. If you convince him, we’ll never know it was your idea. If you don’t, we’ll never know you disagreed. Because, either way, you’ll emerge from the room championing his decision as if it was your own and you’ll execute it with excellence.

13. Don’t break the law. The only decisions you should never champion are unlawful ones: a decision that breaks the law; a decision that will hurt or kill someone who shouldn’t be hurt or killed; or a decision you simply can’t live with. In that case, you’ll have your own decision to make. I hope you never have to make it.

God speed, General.