I'm ex-British Army (infantry), so they are primarily for grunts.
However, a lot can be applied across all armed services.
01. A sucking chest wound ... is nature's way of telling you to slow down.
02. Recoilless rifles ... aren't.
03. Neutral countries ... aren't.
04. Suppressive fire ... won't.
05. Friendly fire ... isn't.
06. The only thing more accurate than incoming enemy fire ... is incoming friendly fire.
07. Incoming fire ... has the right of way.
08. When you are forward of your position ... the artillery will always be short.
09. When the enemy is closing ... the artillery will always be long.
10. Try to look unimportant ... the enemy may be low on ammo.
11. Don't look conspicuous ... it draws fire.
12. Never draw fire ... it irritates everyone around you.
13. Never share a foxhole ... with someone braver than you.
14. Teamwork is essential ... it gives the enemy other people to shoot at.
15. No combat ready unit ... ever passed inspection.
16. No inspection ready unit ... ever passed combat.
17. Fortify your front ... and you'll get your rear shot up.
18. Make it too tough for the enemy to get in ... and you can't get out.
19. If your attack is going really well ... you're in an ambush.
20. The enemy diversion you are ignoring ... is the main attack.
21. If you're short of everything except the enemy ... you're in a combat zone.
22. When in doubt ... empty your magazine.
23. If both sides are convinced they're about to lose ... they're both right.
24. Once you have secured an area ... don't forget to tell the enemy.
25. There's always a way.
26. The easy way ... is always mined.
27. If the enemy is within range ... so are you.
28. Tracers work both ways.
29. In war, important things are simple and simple things are very hard.
30. If it's stupid and it works ... it ain't stupid.
31. Communications will fail as Soon™™™™ as you desperately need fire support .
32. Cavalry doesn't always come to the rescue.
33. Weather ain't neutral.
34. Remember, your weapon was made by the lowest bidder.
35. If you can't remember ... the claymore is pointed toward you.
36. All five second fuses ... are three seconds.
37. Military Intelligence can be a contradiction in terms.
38. There is no such thing as a perfect plan.
39. No plan survives the first enemy contact.
40. Sniper's motto: "Reach out and touch someone."
41. Peace is our profession ... mass murder is just a hobby.
42. Killing for peace ... is like whoring for virginity.
43. Professionals are predictable ... but the world is full of dangerous amateurs.
44. All other things being equal ... the side with the simplest uniforms wins.
45. It's not the one with your name on it ... it's the one addressed "to whom it may concern" that you should be worried about.
46. Mines are an equal opportunity weapon.
47. Smart bombs have bad days too.
48. Don't ever be the first, don't ever be the last and don't ever volunteer for anything.
49. Anything you do can get you shot ... including doing nothing.
50. Once the pin is pulled ... Mr. Grenade is not your friend.